I go to the size and change it (so I get a bigger field to mod with) and I don't get textures. I add some, but nothing happens. Should I just not change the size or can this be fixed.

The terrain is actually there, you just can't see it. As frustrating as it sounds, you're going to have to retexture your entire terrain. Go to the texture button and choose a texture. Then make a 100x100 square brush (biggest area) and paint over the terrain until its all covered.

I've done this. (I'm pretty sure...) I munged it, went ingame, and there was no texture. Just a whole bunch of black.