I couldn't find anything. Please help!
I must be misunderstanding your request.
If you just want to install codeblocks on ubuntu, ubuntu already has GTK on the system. No configuration is necessary.
If you mean you want to compile GTK programs with CodeBlocks, then you will need the GTK_ 2.0-dev packages which ubuntu
Synaptic can provide for you.
If you mean you want to install GTK on windows, search the forum, I believe there was a thread on that.
What OS? What version of CB ? Could you provide more info?