Find the "Raw" URL of the file (as described in Method 1). Then:

Depending on your environment (GUI vs. Terminal), here is how you make the download "work."

hashcat -m 0 -a 0 hash.txt /path/to/rockyou.txt

To get just one .txt file without cloning an entire massive repository: Navigate to the file on GitHub. Click the button to view the plain text.