Update client list

Hello,
I would like to create a update into my project (not a .pak), idealy that made the project grab a .json or .csv file to my server, and then update the players list.
The goal is to understand how to manage the call between my game and my server, to made some update, this project is a fast resolve to win, with a top players in the lobby, so i need a constant update at start for all players who start their game.
Hope my explaination is well writed
Have great days guys !!