When working a multiplayer game you need to be able to quickly test and iterate over your game, there are few ways to do this.
The easiest way to test your multiplayer game is to make a standalone build (PC or Mac) then run the editor and the build at the same time.
This is my favorite way for testing a multiplayer project. You basically have your original project then create a clone out of it the best way to do this is by using by using ParrelSync.
ParrelSync is a Unity editor extension that allows users to test multiplayer gameplay without building the project by having another Unity editor window opened and mirror the changes from the original project.