Purpose

GitHub allows accounts to be configured to use two-factor authentication (2FA). SourceTree can work with GitHub's Two-Factor Authentication model.

Solution

To work with GitHub's two-factor authentication in SourceTree you can simply use your access token instead of your password. The steps to do this are as follows:

1. Go to your Personal Access Tokens settings in GitHub.
2. Click on the Generate new token button.
3. Name the token something descriptive.
4. Select which scopes you wish to grant this token.
5. Click the Generate token button.
6. Copy the token and use it as a password in your hosted repositories.

You can find more information about this on GitHub's help here.