Can you even program at all? It doesn’t sound like it. If not, you can forget about multiplayer and try learning how to program singleplayer and learn the basics of programming. If you don’t want to program, you could either contract someone to do it for you, but in that case I would recommend you to quit game development after all. I’m not trying to be rude to you, but alot and I mean ALOT of people underestimate the amount of time, work and effort goes into making a simple game, even in an engine like Unity.
Though, if you can program singleplayer games already with ease, I would suggest looking at a 3rd party networking solution like Exitgame’s Photon, Smartfox server or ULink ,study their docs, search for online tutorials and try simple things yourself.