Here is a little guide on how to use the logic gates:
Hold the logic gate
Set its source by control right clicking
Place the logic gate
You can view its source coords by hovering over the logic gate
The gate stays open for as long as there is an item at source
Inspector panels can be used alongside the logic gates, as they can detect information about structures and react to it. You can have a panel detect if there is an item inside the press, and a gate that detects if the panel has detected something.
I hope this helps