Can you be more specific as to what you've tried and where you're having an issue?
To adjust the settings you go into the Setting from the menu (or Options at the start screen), Controls, then right to the wheel settings (RB on a controller, right paddle on the wheel). The game should auto detect your wheel, but you can set it if it doesn't. Then hit button 7 on the wheel (you'll have to look up in the Thrustmaster software which button that is, or there should be a corresponding keyboard button) to enter the advanced settings.
Note that you can't change the default wheel button mapping, unfortunately. You can create a custom wheel button mapping by selecting Custom for the wheel rather than your specific wheel type, but I don't recommend that as the custom config doesn't let you reuse buttons the way the default config does and doesn't seem to support any more buttons than the default config.