The error message is telling you exactly what you need to do to fix the issue.
git config --global user.email "email@example.com"
git config --global user.name "Your Name"
Obviously you should replace the values inside the quotes with your own email and name.
EDIT: You can also use the SourceTree Options dialog:
As a project manager, I have discovered that different developers want to bring their previous branching method with them when they join the team. Some developers are used to performing individual wo...
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