If you download a free texture for a particular outfit, the usage rights are normally in the readme. If you download a generic texture that you'd like to use IN your clothing texture, check the usage rights of the site you got it from. Imageafter and the three links I posted above allow commercial usage even if included in a texture map.

If what you mean is how you get the texture on the model when you only have the model, all you need is a copy of UVMapper Classic. That will allow you to create a template for that model on which to paint so that all your textures land in the right places ;o).

Laurie