When UnrealTournament has one or more configurable mods installed, it adds a Mod option to the main menu bar. When XMaps is installed, it adds an 'XMaps' entry to that menu. So - bring up the main UnrealTournament menu, then select 'Mod'. Click on the XMaps entry, and there's the Setup window. There's also an XMaps Client menu option, which opens the XMaps Client Setup window.
XMaps Setup is in three parts - the Setup window that configures the main XMaps features you want to use, the Server Options window that controls the behaviour of your XMaps clients, and the Game Options window where you set up Game Switching options, Extended map lists, Favourites and Mutators for each game type.
Key Bindings and Mutate CommandsXMaps supports several key bindings to control UT while it's running; you can configure these using either UT's Preferences (select Options | Preferences from the UT menu and then the Control tab) or the XMaps Client Setup window. See Commands and Bindings for more information.
The XMaps HUD MenuFinally, while UT is running, you can use the HUD Menu or XMaps Remote Control to configure or change XMaps features and settings.