You can access the Version Control integration from the side panel on the right.  

Expand the side menu by clicking anywhere on it to get more details. The commit tab  is open by default.

In this example, there are 4 uncommitted changes shown. Clicking on the expand icon next to dbo.getCustomers.sql, we can see the differences, which shows we've explicitly listed the columns in this stored procedure instead of using SELECT *.

Once you have reviewed the changes, select files using the checkboxes, enter a message, and then press the Commit button.

This commits your changes to your local repository.  When you're ready, push these changes to the remote repository to share with the rest of your team or kick off a Continuous Integration process.