Logistics network gets plugged into the substation with the arrow for the CARGO REQUEST print. It will send a green signal down to your rocket when a requested item in the bank of combinators is empty. Speakers will also put out alerts when an item is empty if you would rather launch manually.
Lights on the CARGO UNLOAD and UNLOAD TO STORAGE are green when ready to accept cargo, red when unloading.
Lights on the CARGO LOAD blueprint are red when the rocket is any combination of out of fuel, out of sections, or out of capsule. Lights are yellow when loading. Lights are green when a green launch signal has been received via the signal receiver.
All blueprints have a version for orbit and a version for the surface.