1. The search engine is your friend.
2. Copy the AVI file into the simfile's directory.
3. Go into the simfile, and at the beginning of the file (or whereever) press escape and select "Add/Edit Background Changes."
4. Select "Add change to song movie". Scroll left or right until your AVI is highlighted. Press enter.
__________________ Thanks to BemaniStyle for being there. (Donated $6.00)