Setting up the cord on the braid roller: insert one side of the loop through the holes, then slide the opposite end through the end that just went through the holes. In essence you are making a half hitch knot around the roller — similar to what you do when attaching the leader to a tama.
Advancing the braid: you should roll the roller away from you so that a large section of the braid is visible to you to check. The little dowel must be inserted through two holes in front of the stopper. If you insert it behind it, the braid will unravel.