Hmm. You’re typing as if you’re being chased by somebody with a chainsaw, so I apologize if I misinterpret what you’re asking.
If I gather correctly, though, you’ve made a single player game, and now you want to add realtime multiplayer. If this is right, continue reading. If not, you can skip the rest of this post and respond, although doing so coherently while breathing slowly will help dial me in on the right direction.
Sadly, if you’re nearly complete with the game and are only now addressing multiplayer, then I regret to inform you that you’re nowhere near finishing your game. Ideally, a multiplayer game is built from the ground up with networking in mind. I added turn-based multiplayer into a game that was very early in development and it still took a good bit of rewriting.
Luckily, it sounds like you followed a whole bunch of tutorials, so the good news is you probably learned a bunch of stuff, right? So don’t be too sad if it’s easier to throw everything away (figuratively, never delete projects!) and start over from scratch again! I’d even wager that if the game were built exclusively from tutorial guidance, it’s probably not too big of a loss to the industry if that game doesn’t get released. 
For multiplayer, you’ll want to look into a framework like UNET or Photon if you’re not familiar with networking code yourself (and I assume you aren’t, from context). Photon seems to be a popular choice, but as with anything quality, there’s a price tag involved.
If you don’t mind a bit of extra effort, your platforms have native APIs available to handle networking code. A fellow by the name of @prime31 has some great plugins to allow you to interface with those APIs easily. Again, you get what you pay for, and with prime stuff, you get A LOT, so save up some cash.
