Step by Step is nearly impossible or would require hundreds or even thousands of steps and even then not work since every model is different.

The VERY basic version of it is:

• Get a 3D model creation tool (Blender, 3DMax, Maja, or another one[en.wikipedia.org])
  
• Learn how to use the program in general, there are loads of tutorials for that online.
  
• Make your avatar
  
• Give the avatar bones, and name those bones according to the requirements (there is info about the naming requirements in the FaceRig install folder in the "docs" folder.)
  
• Test and tweak the avatar till you are content with it.
  
• Either just use it for yourself, or upload it here to the workshop or on the community made / managed site facerig.us (not to be confused with the site made / manged by the developers of Facerig, www.facerig.com)

If you need help with the steps 4/5, take a look around this part of the forum, or on facerig.us
The first 2 steps you'll have to do by yourself, and the 3rd for the most part too, although there are some pre-made models online of various things that you can use as a base.

thanks that helps alot