You'll need Conda, a Hashtag Basketball account with your league set up already, and a Yahoo Fantasy Sports account. see References for the links. With Conda, you'll need to create a new environment and install the Selenium package.
In Terminal, change directories into the directory containing the .py file. Activate the Conda environment that you made and then run the file with python hashtag_bball_bot.py. When the script is finished, you should have a rankings.csv file in your directory.
Sometimes the script will fail due to a timeout near the yahoo login steps. You can just try the script again.