Arranging tracks

Greetings,
the initial blank setup has tracks 1 and 2 as V2 and V1 and tracks 3 and 4 as A1 and A2. SO when I drag my 1st AV file it occupies either V2A2 or V1A1. How can I rearrange the default startup so A1 follows V1 then A2 follow V2?