I would like to unfork the repositories i did fork, how can i do it?

My user is Trendset-RD (Trendset) · GitHub
I had forked lots of gnustep, gnu/linux and gnu/hurd i wish to use later on.
However, as i’m new to Github, i added them in the wrong way, i had forked several projects when what i intended to do was to add them as submodules for an operating system i wish to build.
I have connection to my repositories via Smartgit, i had learn how to add them as submodules.
How can clear all what i forked at once and start over?

Goto Settings for your forked repo, scroll to the bottom. In the “Danger zone” hit Delete and follow the instructions.