[sysoverload]

add a track is different from add a clip btw. one track can have several clips. you want four tracks, with one clip in each (each edited and chaptered differently). the 'add a track' button is in the top left of the screen. each time you press it you'll see track 1, track 2, track 3, etc.

for a dvd you'll have to add the TS folder 4 different times, so you'll need free space totaling 5 times the space of your dvd (4 temporary files and one output VIDEO_TS folder).

I don't know what else to say other than read tutorials and experiment on your own. It ain't rocket science, especially with such a user friendly program as this.