I agree with Brian, you definitely have to practice though the supplied tutorials and watch the videos (they give you a feel for what's going on within the app and how to use the various toolbars and functions).

Typically an app like 3D-Coat and ZBrush are used to create your texture and displacement maps for loading into your rendering application.

So first you have to be comfortable with working with UVs, and various map channels (color, bump, displacement, specular etc.) within your rendering program.

3D-C lets you create those various map images to be loaded where you plan to render.

The first thing to pin down and get comfortable with is creating the maps in 3D-C and getting them to render properly in your rendering app (Carrara, Cinema 4D, XSI etc.)

If you don't have a rendering app yet, you would need to choose one first before you start working with and learning one of these displacement / painting applications!

-Will