How do you get a cat to lay on a cat bed?

Lure it with food or lock it out of your room. It will get used to sleeping in its bed and not in yours, if you lock it in its room where the cat bed is.

You can either try to just keep putting it in the cat bed right after you give it milk or food because it will probably be sleepy right after eating/drinking (if it's not yet weaned).

Some cats, though, just don't like cat beds, and may choose to sleep in a chair, on a desk, under the bed, etc. if not on your bed. Do not try to force it to sleep somewhere, as this will only cause other problems such as the cat peeing, clawing, etc. in the place where you lock it in, and if you physically force it into the bed, you'll just get hurt. It's just not smart to try to force a cat to do something they don't want to do, and cruel to punish it for protesting.