I’m not sure what you’re asking. To modify boot.cfg (you may see just boot, if so, use this file instead), right click and say “Open With Notepad++”. Then change the address after “AUTHSERVERIP=0:” and the next comma to Jonny’s ip address.
If this still doesn’t make sense, check out the tutorial in the Downloads page.
If you know all this, and did it correctly, check out Jonny’s forum How to connect to server.