How do I Connect Over the Network to an Already Running Scene?

I'm building a multiplayer shooter and right now the player can either host a game or join a game.

The setup so far:

-Main Menu Scene

-Host Game Button

-Join Game Button

-World 1 Scene

-SetupScript

-NetworkManager

By clicking host game, the game loads World 1, sets up a server using the network manager, and spawns a local client player. So far so good. What I cant figure out how to do, is connect to this already running scene and server with the join game button. Anything that creates a client connection needs to run in the scene that's been loaded by the server, but not by the client. How can I connect to an already running scene and server from another scene?