This type of bin is more for creating very nice, finished castings, vice focusing on worm production. Basically, you keep adding material to one side until it is full. Then stop feeding that side. At this point you start filling in the second side, putting the new material next to the full side.
Once the second side is full the first side should be absent of worms, they should all have migrated to the fresh, second side. Take a small hand trowel and remove all the castings from the first side. Repeat process in reverse.
Joe