Help/Driver/Main Menu/Options
From TrainzOnline
Clicking on "Options..." will open up a menu which contains tabs for differnt kind of settings. To access each of them, click on the highlighted rectangles to the left. Each tab contains squares next to a description of a setting. A square with a green tick in it means it is currently enabled. To disable a setting, click on the square next to it, the tick should dissapear.
To the bottom right corner of the menu there are two symbols, a "tick" and an "x". Pressing "tick" will save the changes made. Pressing "x" will cancel them.