When you add a new file to your repository or make a change, you need to stage, commit, and push that change to your remote repository. After you make the change, you'll notice your new file in Sourcetree.

1. From the options menu of the new file, select Stage file.
   

2. Click the Commit button at the top to commit the file.
3. In the message box, enter a commit message.

4. Click the Commit button under the box. You can now see your change under the History tab.

5. From Sourcetree, click the Push button to push your committed changes.

6. Under the Push? column from the dialog box that appears, select the branch where you want to push the change and click OK.