editor help plz

[QTP12345]

ok so i created a song using ddream studios and im trying to but a background video in it. when i add it in the video is off sync to the audio i try to create more lines so the video starts earlyer than the song but the editor wont let me do that ( in stepmania 5 editor ) when i add lines in ddream studio, it shows in the stepmania 5 editor BUT i dont know how to change the SONG START if i can do that then i can start the song at the right time so the video can be in sync with the rest...... plz help!