Body Texture editing and Gimp

[medic975]

Could someone point me to a GIMP tutorial on applying textures via gimp.

 

What I'm wanting to do is I've exported the texture of the UN7B vagina from nif and it gave me a tga file. I'm wanting to apply the textures from the UN7B to the part of it, and then apply my body texture real girls to the surrounding area around the vagina so I can use my real girls texture and the vagina without skin discoloration. 

 

attached is a pic that sunwalker provided me. I'm just unsure of where to go to apply my dds texture to this. Tried googling it, but I'm a little lost in the results.