GitHub is a popular place to host repositories so that many people can work on it collaboratively. Other popular services include BitBucket and GitLab.
Before arriving, you should have created a GitHub account. Log into that account now and create a new repository by clicking the "+" in the upper right.
Name the repository 'planets' and add a description if you'd like. Click the green "Create repository" button and move to the next screen.
Filling out this form effectively runs the following commands on the GitHub servers:
$ mkdir planets
$ cd planets
$ git init
You now have two separate planet.git repositories: one on your local machine and another on the GitHub server. The GitHub repository is not yet connected to your local repository, so we'll remedy that now.
After creating a new repo on GitHub, we are led to a screen that allows us to copy a link to the GitHub repo. Copy this link and run in the terminal:
$ git remote add origin https://github.com/sam-dixon/planets.git
origin is the nickname for our local repository. To send the changes on your local repository to the remote repository, run
$ git push origin master
In the future, you can pull changes from the remote repo to your local repo with
$ git pull origin master
Running this command now won't do anything, since we synchronized our local repo with the remote repo with git push. However, if someone else made changes to the remote repo, you can have those changes reflected in your local repo by running this command.