find the folder and go unity_fps/assets select all the files then hit command-c or control-c.
Next go to the assets folder in your unity project and press command-v or control v to paste it.
It should be done and all the assets should now be in your unity project.
For anyone wondering how you can download these assets and just the assets follow this:
Go to your terminal/ command prompt enter: git clone https://github.com/beaucarnes/unity_fps/assets/
find the folder and go unity_fps/assets select all the files then hit command-c or control-c. Next go to the assets folder in your unity project and press command-v or control v to paste it.
It should be done and all the assets should now be in your unity project.