If you want to use Codeblocks and Graphics.h,you can use Codeblocks-EP(I used it when I was learning C in college) then you can try
Codeblocks-EP http://codeblocks.codecutter.org/
In Codeblocks-EP , [File]->[New]->[Project]->[WinBGIm Project]
It has templates for WinBGIm projects installed and all the necessary libraries pre-installed.
OR try this https://stackoverflow.com/a/20321173/5227589