GUI

Windows
Make sure you have pip installed.
Open a command prompt
Type pip install guizero and press Enter

Mac OS
Open a terminal (you can search for it in the Launch Pad)
Type sudo pip3 install guizero

Linux
Open a terminal
Install tkinter using your distribution's package manager, e.g. sudo apt install python3-tk
Install guizero using pip by typing pip3 install guizero or sudo pip3 install guizero if you dont have superuser rights