Install python3 using the package manager of your choice or by downloading it here. For the manual installation, choose under Downloads your OS. For most users, the 64-bit installer will be the right choice. In there, make sure to check the "Add Python to PATH" option.
Next, we need pip. If you installed python from the link before and downloaded a version >= 3.4, you can skip this. Otherwise, you can find a guide on how to install (or check if it is installed) here. Most package managers offer it separately in a package called e.g. python-pip.
We also want to install PyGame now. An installation guide can be found here.
First, open any terminal application. In the console, enter python -m pip install -U pygame --user.
Depending on the OS you have to replace python by py or python3. It should start downloading and installing all required packages.
At last, we also want to use an IDE. A simple and intuitive IDE is Thonny which can be downloaded here. However, any IDE will work and it is possible to use standalone editor programs without any programming features.
Alternatively, it is also possible to use an Online-IDE like replit.com (requires login).
Download the source code above either via git or the download-button as a zip file.
Next, open the file main.py in your IDE.
If you downloaded the branch demo, you can just hit the Run button in your IDE and enjoy a little demo. Here you can find some optional tasks.
The main branch contains some basic functionality, but you have to solve tasks to get the working dino game. To find them, use the search function and look for comments which contain the word task.