Attach it using zip ties (cable ties, whatever you call 'em), works for most people. As for the hardwire cloth, I don't know any brands, but you should be able to get it at most home improvement stores. And make sure you get a coated wire, galvanized will just soak up pee and you'll have to replace it much sooner.
When I got my hardware cloth, they had a big selection with different sizes. Get the kind with 1/2" squares. Coated is preferable (usually PVC coated, and I think it's usually green), but I didn't have that choice. I've had galvanized on my cage since September, and it's holding up just fine and doesn't smell.
I attached it with wire, because zip ties are plastic and easily chewed off. I'm not sure where to get the wire because we already had it here, but it's thin, easily twisted, and came in a roll, kinda like tape. I also used twist ties in some places, which work just as well. If you do use zip ties you'll have to check them frequently to make sure the rats haven't chewed them off.
zip tie placement greatly affects how quickly they get chewed off as well, by the way. my girls have never chewed on the zipties that hold their own levels up (attached on all sides to the 4 walls = a new level) because they simply can't get to them. zipties on ramps, however may get chewed a little cuz they are exposed. and if you get your rats plenty of other things to chew on, they usually won't chew on those boring things anyway.
Well all right, if everyone else advocates zip ties XD I just prefer the wire because I never have to check it, there's no risk that maybe they might get chewed off and possibly squeeze out and escape, and I never have to buy more to replace it. Personal preference