This provides an introduction to using Rstudio to share files in GitHub
The following are useful resources:
A video walking throught the process for the first time: https://www.youtube.com/watch?v=aM0bjrYCvv8
Instructions for Git/GitHub/R/RStudio set-up and early usage: http://happygitwithr.com/
Rstudio Support: https://support.rstudio.com/hc/en-us/articles/200532077-Version-Control-with-Git-and-SVN