The steps for unwrapping an object are:
- Open your UV/Image Edit area
- Select Edges and Mark Seams (Control E)
- Select All
- Press U key (Choose Unwrap, Smart UV Project, or one of the other choices.)
- Repeat and tweak the above until you get a layout you can work with
Once the object is unwrapped, there are 4 possible methods to put a texture on it:
- Export the UV Layout and paint on it in Gimp or Photoshop or
- Open a texture in your UV/Image Edit Area (usually seamless texture) or
- Paint directly on the texture using Texture Paint or Vertex Paint or
- Use Materials, Textures, and Bake (in either Blender Render or Cycles.)
Once you have your image texture the way you like it:
- Add lights if necessary to see your model.
- Preview in Viewport Shading Render until satisfied.
- Click on the object and choose File->Export->Static (lower left panel) and Export
- In the UV/Image area, click on Image->Save as Image. Name it and save it.
- Go inworld. Choose Mesh Upload, upload the mesh.
- Choose Image upload, upload the image.
- Rez the mesh, choose edit, add the texture.
There are many existing tutorials for unwrapping in Blender. Rather than create a new one, I will point to some good ones. I highly recommend the Born CG Tutorial #13 UV Mapping on youtube.
- The Blender Manual!
- Katsbits.com Learning Unwrapping
- Chocofur.com Exploration of the Unwrapping Methods