If you'd like to walk through git lesson materials that cover setting up git, creating a repository, the add-commit cycle, how to explore your history of commits, how to ignore certain files, how to set up a remote connection to github, how to push and pull from that remote, how to deal with conflicts, branching, and contributing to someone else's repo, then check out:
http://erdavenport.github.io/git-lessons/
We published an article in PLoS Computational Biology a few years ago that walks through similar concepts (including a follow along tutorial that results in you contributing to the paper's repository). Please contribute! Check it out here:
http://journals.plos.org/ploscompbiol/article?id=10.1371/journal.pcbi.1004668
Here is a file that lists my entire command line history from the code review session, typos and all: https://raw.github.com/erdavenport/code_review_2018-02-13/master/history.txt
Here is the link to my 'science' repo on github: https://github.com/erdavenport/science