In case anyone else was wondering, the following solution helped me:
Create a secrets.yml file in your config directory.
In your terminal, type the following command: rake secret. This will generate a secret for you to include in your secrets.yml file.
Add the following snippet of code to your config/secrets.yml file:
development:
secret_key_base: PASTE_YOUR_GENERATED_SECRET_HERE
(NOTE: WHEN TYPING THE ABOVE COMMAND, BE SURE TO ADD SPACES BEFORE "secret_key_base" AND NOT TABS, AS THIS WON'T WORK IN A YML FILE.)
Be sure to migrate your database: bin/rake db:migrate RAILS_ENV=development
Now when you boot up the server and render the application in the browser, you should be good to go.
