How to put the wheel on an angle grinder?
So, I bought this angle grinder, 4.5 inches I think the wheel is. I also bought this wheel for grinding metal. It’s got a threaded hub and a nut on it. But it looks like the nut side is supposed to go against the grinder. And the nut is so thin, that a box end wrench won’t fit in there. So, how is this supposed to be done?
Answers below in Comments Section

Most angle grinders come with a tool to remove and replace the nut. I have had grinders with thin hex nuts, and I have had some with a round nut, with holes in it. The round one had holes in it, and a tool that fit the holes.
I would say, if it didn’t come with a wrench, then the nut side should go out, where you can get a wrench on it. It should work fine either way. The only downfall of running the nut out, is if it hits against metal work often, it will eventually round off the edges of the nut. Even if it gets rounded off though, Vise-grips will usually do the trick.
When you tighten the nut, there should be some sort of button, or slider to lock the shaft while you tighten it as well. You will want to make sure you use it, so that you get the nut tight enough.
I wonder what this bunch of paper with all these pictures and stapled in the middle that says Manual is for because I can’t read Spanish
It’s a reverse thread, and there is a specially shaped wrench to use.
Please look at this supplied manual link, it may not be your brand of grinder but applies to 99 percent of north american made grinders http://toolnet.dewalt.com/Toolnet/OMrepos/0039730A2546844400800003B9D2051F.pdf