How to use powershell across multiple domains to populate a group


I am trying to add AD computer accounts to a security group. I have servers across multiple domains and I have a txt file that I am wanting to use to populate the AD security group. Can someone please tell me how I would go about doing this. This is what I am working with right now:

foreach ($member in (get content "C:\group 1.txt")) {Add-adgroupmember "Group 1" -members $member -ErrorAction Continue -Verbose}

The script runs but it tells me the members are not in the root domain that I am running this from, which I am aware of but I am trying to tell PowerShell to look in all domains in the forest.... Thanks in advance!!
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FOXActive Directory/Exchange EngineerCommented:
You need to change the security group to a global security group in order for it to accept users from all domains
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