It's in Applications / Utilities. Or find it using Spotlight.
Type cd (drag your "interactive" folder into Terminal, and it should produce its path). It should look something like this:
Add your changes:
git add -A
Commit your changes with a specific message saying what you changed:
git commit -m "your commit message here"
You can also check the status of what is to be committed:
Once everything looks good, type:
You should receive a successful message.