In this example first we need to get the service using Get-SCSMObject and Get-SCSMClass. The class in this case is System.Service (that will get all services created in SCSM and imported from SCOM. In this case I chose to get the object using the display name. You could get it in other ways using other properties too.
Then we need to get the related object using the Get-SCSMRelatedObject cmdlet. We pass the service as the source object and specify the GUID for the System.ConfigItemOwnedByUser relationship type.