A lot of Lisa's messages on this forum will help you.
For a shape to work in SL, you need to get the texture map right. Lisa's fish has an example:
http://www.independentdeveloper.com/...rom_existing_3
Have a look through the forum though, there's quite a bit on this.
It's always best to start from the sample SL objects that come with AC3D (in the models/sample folder). Look at the TCE for these to see how the mapping covers the full area.