Reddit, what do I do with this pregnant cat?

Someone who moved out of our apartment building several weeks ago apparently left their cat behind. It's just been laying out on a balcony in the heat (we live in Phoenix). We're going to try to take it in, so it can give birth inside where it's cool.

What should we do to make it comfortable? I was thinking about putting a lined box in the back of my closet and setting her in there with food and water, is that the best course of action? Also do I need to help the mother at all giving birth?