You will need a skillshare premium account to access premium content. This script will not handle login for you.
Log-in to skillshare in your browser and open up the developer console. (cmd-shift-c for chrome on mac)
Use it to grab your cookie by typing:
document.cookie
Copy cookie from developer console (without " if present)
Replace cookie.txt file with the copied cookie
Run pip install -r requirements.txt
Then run python skillshare-dl.py "course-link"