Fill the bag with the correct feeding, fill the chamber half way by squeezing it and then open the roller clamp til it reaches the end. This set up does not look like it connects to a pump so you will have to do the math to figure the drip rate or is this used for bolus feeding ?? All of our TF are on a pump so the set up looks different.
Please consult with someone on your floor, NM, charge nurse or educator to find out the policy at your facility. Asking questions is good but each state/facility has specific ways of doing things.
No question is dumb when it comes to pt safety and please do not hook this up to an IV (yes, it has been done).
I can't tell from that picture if the bag has the part on the tubing that you can pull down on to prime it. Most bags/pumps that I've seen have an option to prime it by hand or via the pump. With the bags I used in the hospital, I would fill the bag with formula, squeeze the drip chamber until it was half way full and then pull on the part of the tubing that wraps around the pump until the formula reaches the end. The pumps I use in home care have a prime option so you'd fill the bag, load it on the pump and then hold down the prime key until the formula reaches the end.