Commiting local changes
A commit does not push your changes to the server. Rather, it creates a local point at which you can revert, restore and reset changes. With GIT, it is encouraged that you make regular local commits for this reason. Each task will often have its own commit as a point of reference. To add files using SourceTree, open up your project. Under unstaged files, add all uncommited / modified files. Add a verbose comment and then click "Commit".