Electronics - so I need to disconnect them from the battery?

Howdy need a quick question answered and possibly some guidance when it comes to the speakers and lighting in my van. i’m converting my 1976 Ford E1 50 van and I need to take the paneling that exists in here off but the speakers and a few lights are screwed into the paneling I have absolutely no idea how to disconnect them from the battery or their wiring. Could somebody please tell me where to begin in very simple terms. Thanks very much.