Code for switch servers

Hi there,
I'm coding my Lobby System (1.12.2 Craftbukkit), I'm using BungeeCode and want to code my navigator.

When a player clicks on for example on the Citybuild Icon he should be "redirected" on the citybuild server.

Which function can i use for this?

Thanks!

Edit: Please move my question to Bungee Cord Plugin Development