You can enter textual information about the airfield's circuit pattern into that field and SkyDemon will make it available in the airfield information. You cannot create vector circuit diagrams using that tool.
You can share your custom data with your friends or whoever you like. If you wanted the airfield included for everyone, though, the right action is to contact us so that we can make contact with the airfield owner and add it officially.
You can add your own user documents which match your airfield's ICAO (or other in 3.8 version) designator and they will show up next to the airfield.
You cannot georeference your own charts in SkyDemon.