Comment by tom_

Yeah, git clone --recursive is the main thing I suggest. But unlike Google I include the exact command that you can copy and paste into the terminal to clone the specific repo in question.

And if you're reading the README after cloning it already, there are instructions for sorting that out too, also suitable for copy and paste.

Or if you downloadeded the ZIP from GitHub - I'm sorry. But you won't be left too confused, at least you won't if you read my README, because my README covers this situation as well.

(Also: don't forget to git submodule update after changing branch! But if you're noting everything my README tells you, you won't.)