WSUS Computers exported: Filter that CSV file with Powershell in import

Hello I need to filter a .csv file with powershell.
I exported the information like this:

Get-WsusComputer -ComputerTargetGroups "group" | Export-Csv -Path "C:\export.csv"

but Get-WsusComputer adds more information into that .csv than I need, I only want the "FullDomainName" so I can add those computers to a new AD-Group.
Therefore I need to filter for only the header "FullDomainName" when importing. how do i do that?

I tried this:

Import-Csv "C:\export.csv" -Delimiter "," | select "FullDomainName"

but when doing that and trying to print out the imported values, the imported values look like this:

@{FullDomainName=blablabla.de}

Im quite new to powershell, but to my understanding that import would not be right this way to after that be used to add those fulldomainnames to a new AD-Group.

Thanks for your help!

Assuming the FullDomainName contains the FQDN of the target machines (eg. computer01.child.domain.tld), loop over the names and split them into a name and domain, then query AD like this:

$computerFQDNs = Import-Csv "C:\export.csv" -Delimiter "," |ForEach-Object {
    $name,$domain = $_.FullDomainName -split '\.',2
    $computerAccount = Get-ADComputer -Identity $name -Server $domain -ErrorAction SilentlyContinue
    if($computerAccount){
        # Computer account found, add to group
        Add-ADGroupMember -Identity myGroup -Member $computerAccount
    }
    else {
        Write-Warning "Unable to find computer account '$name' in domain '$domain'"
    }
}

The -split '\.',2 operation will take the input string and split it at the first . (ie. computer.domain.tld -> computer and domain.tld)