It’s kind of hard to find anything that shows you end-to-end multiplayer development. I had to learn piecemeal. Just head to YouTube, search for “UE4 replication” and treat it like you’re binge-watching Netflix. Skip stuff that doesn’t help but remember them in case they are relevant later. Along the way, keep your project in mind so you’re always hunting for things you will need. Maybe take notes – if you’re organized (I’m not). Then experiment and ask more questions here.
But most of all: treat this as a long-term project. Be patient. Be comfortable with being confused sometimes. You will eventually have an intuitive grasp on replication. After that you will be unstoppable. 