Make sure you have conda and python installed https://docs.anaconda.com/anaconda/install/
If you don't have add the force channel to conda conda config --append channels conda-forge
In the same directory you have rl_env.yml open a shell and run the command:
conda env create -n rl_env python=3.7 --file rl_env.yml
NOTE: For windows only. not needed for this tutorial. If you want to install the ‘Atari” enviroment please follow these instructions instead: https://towardsdatascience.com/how-to-install-openai-gym-in-a-windows-environment-338969e24d30