How to add user to one to many groups in Active directory using powershell

Hi  All

I am working on a script to create a user and based on user type i would like to add that user into 2 to 3 groups . At the moment i have 3 groups e.g domain users, Developers, tester, 

$NewUser = Read-Host "New Username"
$firstname = Read-Host "First Name"
$Lastname = Read-Host "Last Name"
$NewName = "$firstname $lastname"

$Group = "Dev"

New-ADUser -SamAccountName $NewUser -Name $NewName -GivenName $firstname -Surname $lastname -displayname $Newname -UserPrincipalName $firstname@handmade.local -Path "CN=Users,DC=mydomain,DC=local" -AccountPassword (ConvertTo-SecureString -AsPlainText"Password" -Force)  -Enabled $true 
Add-ADGroupMember -Identity $Group  -Members $NewUser

I am not sure how to give user(sys admin) this option of choosing 1 or more groups while creating new user