Create a git repository on https://github.com to put the work you've done so far on the course. Initialise it with a README.md and an R-specific .gitignore file.
Edit (and commit) the README.md with a summary statement of some sort describing what the repository contains.
Add the work that you've done from the course; to date, that will be the coding from https://tomstafford.github.io/psy6422/coding-principles.html and the markdown from https://tomstafford.github.io/psy6422/rmarkdown.html
Use git branches to tag the work (say as Chapter5 and Chapter6, so that you could see a version of the repository with only the coding work from the first assignment, or a version with both of the assignments.
Improve your code(1) on the Chapter5 branch, commit the changes on that branch (not on master) and git push that branch to github.com. Tag the finished state of that branch with ANOTHER branch (Chapter5Polished).
(1) Is your code perfect? If so, then just add a code comment saying it's already perfect!