trackmotion or pan/crop. Also use compositing. I'd recomend checking the online manual or the PDF because I always forget how to propperly composite & get it backwards. :D
OK let's do it over here . . I'll stop the Jeteditdv thing .. .
If your background in Track 1 is a solidish colour - say white - then apply the Chroma Key FX to the event on track one. In the Video Event FX Menu that appears, select Track 1's background colour to be removed - I use the "eye-dropper" - and the Flames on Track 2 should appear through the chroma keyed-Out colour on track 1.