I've been having a problem I've asked four people for help with, but I also want help understanding it. For some reason no explanations make sense so I'll ask here. 

I got fucked up normal maps from funny orc game, and I need to fix them. I have CS5.1, 2020, Gimp, and imagemagick. No matter what I do, I don't seem to be able to swap out the channels like I'm supposed to and it's like I'm missing a clear key part of how.

I know the alpha channel is supposed to go into red, and according to K the blue is to be whited out. I've spent the better part of a day just trying to figure it out in all these things, and it makes me feel like I'm back in school because I'm stuck on what is essentially a really easy problem. And the problem is the steps taken. I know what I'm supposed to do, just not how to do it.