,Hello I wanted to make a multiplayer game. Like a scavenger hunt game , i need help on setting up the item and when one of the players finds it and collects it , he wins the game , please help

Making a multiplayer game

I think you should try to start more basic. Besides, there are plenty of tutorials around on how to create a game from start to finish where you will learn everything you need during the process.
Learn the editor and the blueprint system. Look at a few tutorials and read some of the Unreal documentation.

This sounds fairly basic, if it weren’t for the addition of networking into the equation.
There are a fair few tuts around on the subject, but it takes a bit of time to get used to and implement correctly.

If you’re intent on doing this now, then take a look at this: UE4 C++ Server and Lobby System WIP #2 (With source code) - YouTube
Following the link provided in the video’s description, you can download their source code for setting up a lobby that allows players to join your online game.

There’s more to it than that, but it should at least get you started.

it doesn’t sound as though you are particularly experienced with the engine, and if that is the case, then I highly recommend following the advice given by Raptocore first!