Click on the .ipynb file
Download this repository as a ZIP https://github.com/meevans1/how-to-rediscover-the-higgs-with-photons/archive/master.zip
Unzip the file in the Downloads folder on your computer
Open a Jupyter notebook using your favourite Python (3.6 or above) environment (mine is Anaconda)
Click on the .ipynb file (either the original one you downloaded or your version that you downloaded)