Install git for MacOS users

MacOS users familiar with the commandline can use the git client
MacOS users looking for a GUI client should try Sourcetree

Download and install Sourcetree

Download Sourcetree
Sourcetree is downloaded in a zip file. Expanding the zip file will reveal Sourcetree.app.
Drag Sourcetree.app to /Applications

Launch Sourcetree

Do not create BitBucket account

Set the display name and eMail address used when making a commit with Sourcetree

Authorize Sourcetree to access GitHub

Open the Preferences
On the accounts tab, add a new GitHub account.

The GitHub website will launch. Authorize Sourcetree to access GitHub using OAUTH.

After a successful connection, Sourcetree will display a list of available repositories.