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

1. From the options menu of the new file, select Add 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 section.

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

6. From the dialog box that appears, click OK.