should always check the help for programs on howto use thier bulidin UV Map | Texture Editor, because Amapi is just the latest incarnation of 3D Canvas, Carrera is actually a pretty good CG tool.
Oftenly people ask here before even bothering with the help, and as Canvas had a pretty good help on howto use the texture editor it seems a tiny hard to think that amapi doesn't
Kinda why i think its amusing that everyone is crying out for a decent help file, cause not many people used the last one

Whatever program your using just checkout the help first, using keywords for what your working on ...
in this case UV, Mapping, Textures, Skinning etc.
I would resort to Mappers like LithUnwrap and UnwrapperEx only if there is no decent help. Even then there isn't really any good help files for these and i don't doubt you'll be back here wondering what to do in that
Anata aru kowagaru no watashi! 