The underlying structure for Win32 resources in any IDE is the .rc file. In Code::Blocks, if you add a file with the .rc extension to your project, it will be compiled with the resource compiler and linked into your program.
Unfortunately I've never come across a good reference for the structure of a .rc file (maybe someone else can chime in here?); I just learned by looking at the contents of the files Visual Studio produces.
Also, I've started using wxWidgets for all my GUI development, which sits on top of all the Win32 functionality and uses a different format for its resources, and is in my humble opinion far and away easier to work with.