MicroPython is a version of the Python programming language designed to work on microcontroller boards such as the Raspberry Pi Pico.
To install MicroPython on your Pico W first download the latest version onto your computer from here.
Make sure you download the Pico W version if you have a Pico W and the non W version if you have a non W Pico!
With the Pico unplugged from power, press and hold the BOOTSEL button.
Then plug the Pico into your USB cable connected to your computer. You should see the RPI-RP2 drive appear on your computer (use Windows Explorer or Mac Finder to see it), e.g:
Now drag the UF2 file you downloaded to the RPI-RP2 drive. The file will be downloaded to the Pico and the drive will disappear from your computer.
I’ve provided examples to go with the subsequent MicroPython worksheets. You can download this code from here.
If you want to try all the example recipes you can copy this entire set of files to your pico.
Here are the official getting started guides. Note that the blink LED project won't work on the Pico W.
Getting started with Raspberry Pi Pico