How can I get my cats to accept my new iguana? And is it okay to leave them alone together when....?

I have a bearded dragon and I also have a cat that loves to bring dead animals to my front step. My cat likes to sit on top of the dragons cage with her tail swooshing back and forth and yes if I allowed her to have access to my beardie my beardie would be dead. As long as you have a screen top on the cage you shouldn't have a problem. They have little hooks on them so it isn't like the cat is going to knock the top off. If you don't have a screen top then go to your local pet store and pick one up. They aren't expensive. It really shouldn't do anything to affect the iguanas temperament and over time your cat will realize it isn't going anywhere and will pay less attention to the iguana as your iguana will pay less attention to your cat. The best thing you can do when the cat is paying to much attention to your iguana get a spray bottle and fill it with water and every time you feel your cat is trying to intimidate the iguana spray her so she will run away from the area. I hope this helps.