It is very simple to get started with Visual Studio XGen.

1. First you have to download Visual Studio XGen and install it.
2. Now when you start Visual Studio you will have two new menu items in your tools menu.
   
3. Visual Studio XGen transforms XML files using XSLT, as specified in xtransform files. The format of the xtransform file is simple. It basically just defines how to transform an XML file by defining the XSLT file to use and the name of the output file. And parameters to be used by the XSLT file if you want that. For a quick explanation of how this works you can take a look at this example. For a complete description you can look at the xtransform page.
4. You can now click on Tools -> Transform. It will iterate through all items in your solution and look for xtransform files (with extension .xtr.xml) and process them. If an output file was generated that isn't already in your solution it will be automatically added.

And that's it. You can now compile your project.