I need help modifying a script

I've been using this script to add domain users to local computer groups one at a time but I've been tasked with adding the primary user of the computer to the Remote Desktop Users group on their computer.  There are over 100 users and computers.  I am hoping I can pull the data from a csv or text file but I'm stumped.

Here's the script I've been using.  Any help would be greatly appreciated.

$group = read-host "Enter Security Group"

$user = read-host "Enter username"

$pc = read-host "Enter computer name"

$objUser = [ADSI]("WinNT://DOMAIN/$user") 

$objGroup = [ADSI]("WinNT://$pc/$group") 

$objGroup.PSBase.Invoke("Add",$objUser.PSBase.Path)