When you first get your holster, it will be tight. The best way to break the holster in is to use the bag it came in.
First make sure your gun is unloaded and safe. Place the gun in the bag, and holster the gun. Let it sit for a minute, and un-holster it. Now try to holster the gun without the bag and see how it fit's. If it's still to tight repeat the steps as many times needed. Once you do that a few times, holster the gun (without the bag) and try it on. Try to draw the gun from the waist, and see how it feels. Even after using the bag it will still be tight drawing from the hip. Once you can draw the gun with out yanking your pants off, just continue doing draws until it's comfortable.
(Quick Tip) for guns with 4-5 inch barrels. Sometimes it is better to take a piece of seran wrap about the size of a half sheet of paper and fold it to the width between the end of the trigger guard, and the tip of the barrel. Wrap that around the barrel and use that instead of the bag. This will stretch the holster around the barrel without loosing the retention of the trigger guard.
Belt loops: The snaps on the loops are one way snaps. To fasten them, you have to put the bottom of the female snap on first. Then press the top of the snap to fasten it. Then un-fasten from top to bottom.
As always, if you have any questions about break in, let me know.