Help with uv mapping

Is there a tutorial on UV mapping? I’m new to this and can’t really get far. I know how to apply textures to faces but I got a problem with it being on the wrong side(even though double sided is on). Also how do I unstretch a texture? I got a rectangle face but I want a square texture to stack up the rectangle not be stretched.

Thanks, High6.

beginner’s guide:

a more advanced tutorial:

The first one should be really helpful to you. Enjoy.