I have used the TruCatch trap quite often. The setting of the trigger is tricky, but you will learn with time. This video not only shows you how to use this style of trap, but it also shares some trapping basics. Don’t forget the carabiner to lock up the back. I would NOT suggest putting paper down on the floor because the cats will shred it up, quickly, and if they poop or pee right away, it could make it hard to clean. I use a small container for the bait at the back. We each have our own way of doing things, but we wait until the cat has settled down some to put a pee pad inside the trap. Remember, cats need to be fasting for neutering surgery, so you may have them for a bit of time. Okay, the video:
https://www.youtube.com/watch?v=lThK2KP8uMQ