During our Haskell Prime lunch meeting at ICFP, I promised to create a detailed step-by-step guide for creating Haskell Prime proposals on GitHub.  The instructions are now available here:

 https://github.com/yav/rfcs/blob/instructions/step-by-step-instructions.md

Please have a look and let me know if something is unclear, or if I misunderstood something about the process.

Cheers,

-Iavor