If you take your first photo and name the rollers (bars) 1, 2, and 3 from left to right.
When you put your machine on the carriage, the bar #1 will be inside the throat of the machine.
You load your backing wrong side up. The to attaches to the #1 roller and the bottom to #3. Roll it up onto #3 so that the fabric goes over the bar not under.
Your top gets mounted onto roller #2. mount it right side up and roll it so it goes under the bar first.
You slide the batting between #2 and #3. Pull it through and line it up with the top of your backing where it's attached to #1. then unroll the top enough to bring the top edge close to #1 . Either baste, pin or machine baste the three layers together right beside the edge of the leader on #1. Then you're ready to go.
It is very important to roll the fabrics onto the rollers straight. To do this mark the center of all your bars. Then mark the center of the leaders.
Find the center of the top edge of the backing and pin it to the center of the leader. Finish pinning or basting the top edge to the leader. Then do the same to the bottom edge. As you roll it up onto #3, make sure it's tight, and straight every 6" or so. Once you have it all rolled up it should be taught. To roll your top fabric straight, again find the centers top and bottom. Pin the top edge to the leader on #1 temporarily. Then attach the bottom to #2 and roll it carefully as you did the backing. Once it's rolled up, you unpin it from the #1 leader and leave it free until you have the batting in place.
If you have another bar at the front bottom, it's for the batting, but using that is optional. I let my batting hang down when I quilt because I don't want to pull and stretch it.
Good luck = and have fun.