Building Android/Ios multiplayer game

im working on new project is to create multiplayer game for both platforme android and ios the problem i dont find a lot of information about creating and setup my project for multiplayer game connection with other user and more future every online game shold have i read some doc in google console i find just for unity

You will depend on a third party service provider like Photon, PlayFab, Gamesparks or others.
Each service offers their own implementation. Check their websites for implementation with Unreal Engine. Usually they offer a plugin for the engine.