I would suggest that you carefully read ALL the Tutorials of Ashley first about Multiplayer, since Multiplayer is quite the challenging thing to do. I was stuck a week with it before I understood the most part of it.
https://www.scirra.com/tutorials/892/mu ... 1-concepts
The biggest difference in Multiplayer Games compared to Single Player games is, that the HOST Player(Peer) has to do the most part of the Game Logic. The Joining Players would only have a kind of preview of the game itself since the Work is done at the Host Side. This means you have to carefully seperate Host Events and Peer Events, while also maintaing Events that MAY be similar to both the Host and the Peer.
It is quite challenging...
And about bullets(Like moving Objects and no HitScan Weapons), This is a thing you have to approach yourself after you have succesfully understood Multiplayer. The Problem here is the Internet itself.
If the host handles the spawning of Bullets, the Player on the other side may be spawning the Bullet half an second later than he would think(and It may look awkward). That would be annoying.
If Hosts and Players are handling the Spawning, ONLY the Host would look if another Player has been hit by the Bullet. The Problem here is, while the one, starting the shooting, maybe thinking he hit another Player, he could be not hiting the Player since the Bullet would be appearing an second AFTER you actually Shot. The Player would be standing elsewhere. Also the Player which has been hit, and damaged on the HOST Side, may not see that he was beeing attacked.
I hope that this was helpful a little.