Try something like this, it will start from the displayname of a pool
$poolName="My VDI Pool"
$poolId=Get-Pool-DisplayName$poolName|Select-ExpandPropertypool_id
Get-RemoteSession-Pool_id$poolId-State"CONNECTED"|
Select@{N="Desktop";E={$_.DNSName.Split('.')[0]}},Username,State,Duration|
Export-CsvC:\view-report.csv-NoTypeInformation-UseCulture