If you are new to git and working with a team on a Unity project managed in git then this is the place to start:
Getting Started (Markdown)
If you are a contributor to this project you must only add assets that are public domain or open source. Do not add copyrighted material. If an asset you add is not public domain you must add it to the attribution list when the file is added to the project. Please add a URL to where you got the file that shows the license tied to the specific file in case it is necessary to check license in the future.
An attribution list for assets add to this project can be found here: Attribution List