Set Attribute for AD User
Import-module ActiveDirectory  
$csv = Import-Csv C:\temp\ADNew.csv 
Get-ADUser -Filter * -Properties EmployeeId | select Name, SamAccountName, EmployeeId | Sort-Object Name | Export-Csv C:\temp\employeeid.csv
$csv | % { 
    $User = $_.SamAccountName
    $ID = $_.EmployeeID 
    Set-ADUser $User -employeeID $ID 
} 
OR
$allusers = Get-ADUser -Filter * -Properties DisplayName,GivenName,Surname -searchbase "OU=Test Accounts,OU=Users,OU=Domain,DC=Domain,DC=local"
$allusers | % {
    $user = $_.UserPrincipalName
    $givenname = $_.givenname
    $surname = $_.surname
    Set-ADUser $_ -Replace @{url="www.domain.com/$($givenname)-$($surname)"}
}
Add custom attribute:
- Get-ADUser test.user.teams.01 | Set-ADUser -add @{"msRTCSIP-DeploymentLocator"="SRV:"}