Most atomizers come with primer in them. It's not going to hurt you but, it doesn't taste very good. It's a good idea to blow as much as you can out. So a couple hard blows from the end you suck on with some tissue or something over the other end is a good idea. You're still going to have to vape through a little though. It just won't take as long.
I've never used anything but, atomizers on my Reo. However, experience from when I did use cartos says that you do need to fill them first. If you want to use them immediately, you'll do better if you get a syringe to inject the juice down in the filler. I get mine at TSC (Tractor Supply Company). You're around here, I'll PM you where one is. While you're using it, you'll need to squeeze some juice into the carto on occasion to keep it wet. There are no rules on that. You'll just have to learn.
You bought some good equipment. Now you have to learn to use it in a way that works for you. Unfortunately that can be frustrating. The good people on here will help if they can but, you still have to work your way through it. It's worth it though.