Create a new Windows Application, drag a RadControl, i.e. RadButton, from your Toolbox to your form.
Create a new custom theme and save it somewhere on your hard drive (save it as XML files).
Right-click the project node in the Solution Explorer, choose Add >> Existing Item and add the custom theme file(s) together with the theme repository file. This will automatically copy the custom theme file in your project's directory. You can also add a new folder (Add >> New Folder) to place your theme files.
Set the custom theme's Build Action property to Embedded Resource.
Add a RadThemeManager to the form.
From the RadThemeManager's Action Menu (click the Smart Tag to open it) choose Load Theme from resources.
You will be prompted to enter the resource location. C# and VB.NET compilers differ from one another, so:
In a C# application the pattern is ProjectDefaultNamespace.ContainingFolderName.ThemeFileName.Extention if the theme file is in a folder as mentioned in step 3, otherwise it is just ProjectName.ThemeFileName.Extention
In a VB.NET application, it does not matter whether the theme file is in a folder or not, the pattern is always the same: ProjectRootNamespace.ThemeFileName.Extention.
Perform the same action for all theme files needed and also for the theme repository.
Build the application. This will include the custom theme file in your assemblies.
Now you can apply the theme to the RadButton.
To be sure about the theme resource location in step 7, you can use Reflector. After building the project simply reflect the built assembly/executable and you will see it.
If the form with the theme manager will be opened multiple time in the life cycle of the application, the theme manager needs to be diposed explicitly. A suitable place to call its Dispose method is the Closing event of the form.