Tools > Texture Coordinate Editor opens up the texture editing tools. This tool will let you make the "templates" (uv map) for your model. There's a second tool, appropriately called UV Map, than can also be found on the Tools menu that will let you do some fancier mapping modes.
I found this video the other day, you might find it helpful:
http://video.google.com/videoplay?do...18320165998532
Remember for SL, your uv map can't have an holes or gaps in it. It has to be like one big rubber sheet stretched over the whole object. The default shapes that come with the plug-in are already mapped this way; you might find it helpful to open the shapes in the Texture Coordinate Editor and look at their maps for hints.
Whether or not you need to add more triangles depends on the model and your personal preferences. Basically, if the UV mapping is too tricky, you can add more triangles to help yourself out. For example, you'll see some corner cuts in the default cube just for that purpose. But you don't need to add triangles as long as you can get the map right. The map is the part that matters.
Another tutorial:
http://www.independentdeveloper.com/...rom_existing_3