Make sure you’re logged in.
Then, on the album page, click the yellow Edit button, approximately here. That’ll take you to the Edit Album page, where on the left-hand side you’ll see your track listing.
When you roll over a track in the list, you’ll see a square icon that looks like three horizontal bars. Click and drag that icon to move the track up or down within the list.
When you are satisfied, click Update, and you’re done.