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This is an example in PowerShell of how you can schedule the installation a software package by Altiris DS.
Instead of using the API, the command-line tool axsched is being called to schedule the software package.

function DeploySoftware
{
	param( [String] $pcname,  [String] $package,  [String] $nexttime,  [String] $folder)
	#Write-Host "Deploy $pcname '$package' /t $nexttime /f '$folder'"
	#\\ALTIRIS\express\axsched.exe "$pcname" "$package" / t "$nexttime" / f "$folder"

	$StartInfo = New-Object System.Diagnostics.ProcessStartInfo
	$StartInfo.CreateNoWindow = $true
	$StartInfo.UseShellExecute = $false
	$StartInfo.FileName = "\\ALTIRIS\express\axsched.exe"
	$StartInfo.WorkingDirectory = "C:\Temp"
	$StartInfo.Arguments = "`"$pcname`" `"$package`" /t `"$nexttime`" /f `"$folder`""
	$p =  [System.Diagnostics.Process] ::Start($StartInfo)
	$p.WaitForExit()
	if ($p.ExitCode -eq 0) { $TRUE } else { $FALSE }
}
#This function adds a number of minutes to the given date time and outputs the addition in the right format for AxSched.
function Get-ScheduleTime
{
	param( [System.DateTime]  $starttime,  [int] $minutes)
	#$minutes = 12
	$tspan = New-Object System.TimeSpan(0, 0, $minutes, 0)
	$addtime =  [System.DateTime] ::op_Addition($starttime, $tspan)
	#"2008-10-20 15:00"
	$y = $addtime.Year
	$mo = $addtime.Month
	$d = $addtime.Day
	$h = $addtime.Hour
	$mi = $addtime.Minute
	$schedtime = "$y"
	$schedtime += "-"
	$schedtime += TwoDecimal("$mo")
	$schedtime += "-"
	$schedtime += TwoDecimal("$d")
	$schedtime += " "
	$schedtime += TwoDecimal("$h")
	$schedtime += ":"
	$schedtime += TwoDecimal("$mi")
	$schedtime
}
#Simple function to convert a single decimal to a two decimal, eg 7 becomes 07
function TwoDecimal
{
	param( [String] $Number)
	while ($number.Length -lt 2) { $number = "0$number" }
	$number
}
$now =  [System.DateTime] ::Now
$pcname = "COMP007"
$jobname = "Install Outlook 2007"
$jobfolder = "Software"
#The installation of the package needs to be started after 5 minutes.
$nexttime = Get-ScheduleTime $now 5
DeploySoftware $pcname $jobname $nexttime $jobfolder
 

The web-interface of Altiris Notification Server can sometimes be a bit sluggish.
Certainly if you have to add a computer to 10 or more collections.
To speed things a bit up I have written this Powershell script, which uses the Altiris ASDK to perform queries to Altiris NS.
This script was intended to ensure that a new workstation receives the same software as the old workstation.
It also can be used to just clone the software of a workstation to a new workstation.

#Active Directory Domain
$domain = "LCODE"
#Host name of Altiris Notification Server
$nsserver = "ALTIRISNS"
#Major resource collection
$maincollection = "LCODE Software Collections"
#Sub resource collection
$softinstallcollection = "Software Installation"

#This is a schematic of the structure maintained in Notification Server
#The major resource collection is a child of Software Management
#The name of the sub resource collection is just the first part of the full name (Software Installation)
# as this is being matched with the children of the major resource collection
# all children beginning with that name are being enumerated
# eg. "Software Installation" causes "Software Installation 1" and "Software Installation 2" to be enumerated
#
#Resources tab
# Resource Management
#  [-]  Collections
#       [-]  Software Management
#            [-]  LCODE Software Collections
#         [-]  Software Installation 1
#             []  SW Package 1
#             []  SW Package 2
#         [-]  Software Installation 2
#             []  SW Package 3
#             []  SW Package 4
#

#Load Altiris ASDK
$coll = New-Object -comObject Altiris.ASDK.NS.CollectionManagement
$item = New-Object -comObject Altiris.ASDk.NS.ItemManagement
$res = New-Object -comObject Altiris.ASDK.NS.ResourceManagement
$report = New-Object -comObject Altiris.ASDK.NS.ReportManagement

#Establish connections to Altiris Notification Server
$report.targetserver = $nsserver
$report.authenticate()
$item.targetserver = $nsserver
$item.authenticate()
$coll.targetserver = $nsserver
$coll.authenticate()
$res.targetserver = $nsserver
$res.authenticate()

#Retrieve GUID of the Major resource collection
$maincollectionguid = ($item.getItemsByName($maincollection)).GetValue(0).Guid

#Ask user to enter hostnames of old and new pc
$oldpc = Read-Host "Old PC"
$newpc = Read-Host "New PC"

#Retrieve GUIDs of computers
$oldpcguid = $res.getComputerByNameAndDomain($oldpc,$domain)
$newpcguid = $res.getComputerByNameAndDomain($newpc,$domain)

#Check if we don't have an empty GUID for one of the computers
if(($oldpcguid.length -gt 0) -and ($newpcguid.length -gt 0)){

#Retrieve all software collections
$softwarecoll = $item.GetItemsInFolder($maincollectionguid) | foreach-object -process { $item.GetItemsInFolder($_.Guid) | where-object { $_.parentfoldername -match $softinstallcollection } }

#Enumerate all software collections
$softwarecoll | foreach-object -process{
$softguid = $_.guid

#Check if OldPC is in software collection
$result = $coll.getinclusions($softguid,"Resource") | where-object { $_.name -eq $oldpc}
if($result -ne $null){
$softname = $_.Name

#Display and log that OldPC has this piece of software
Write-Host "$oldpc $softname"
Add-Content ".\$newpc.txt" -value "$oldpc $softname"

#Add NewPC to software collection
$coll.addinclusions($softguid,$newpcguid)

#Check if NewPC is in software collection
$result = $coll.getinclusions($softguid,"Resource") | where-object { $_.name -eq $newpc}
if($result -ne $null){

#Display and log that NewPC has this piece of software
Write-Host "$newpc $softname"
Add-Content ".\$newpc.txt" -value "$newpc $softname"
}

#Refresh the software collection
$coll.updatecollections($softguid)
}
#Write-Host "Result:$result"
}
}else{

#One of the GUIDs could not be found. Most likely computername is wrong or it does not exist in Notification Server
Write-Host "Problem finding GUID for Old/New PC"
Write-Host "Old PC: $oldpcguid"
Write-Host "New PC: $newpcguid"
}