Just double click on the 'main.pyw' file to run it!
It uses Tkinter, which should be available with a standard Python install. If not, for example if using a Linux, it may be available in a package such as python3-tkinter.
Each level has an increasing number of balls, starting with 2, and each level resets the number of lives depending on the number of balls. You right click to determine whether to grow the wall vertically or horizontally, and click to create a growing wall in said direction. If the wall, while growing, gets interrupted and hit by a ball, that side of the wall disappears and you lose a life. Empty boxes get filled in automatically, which counts towards the total fill percentage.