Insert the microSD card into your computer and install the right Raspberry Pi Imager for your operating system. You can do this with the following links:
Once this it has downloaded install and open the application. It should look something like this:
Open the “CHOOSE OS” menu, scroll down and click “Ubuntu”.
You will then be able to see a list of Ubuntu downloads to choose from. For this tutorial we recommend you select the Ubuntu 18.04 download. As indicated in the imager this will work for the Raspberry Pi 2,3, 3+ and any of the 4’s.
Select the image you want and open the “SD Card” menu. Select the microSD card you have inserted.
Finally, click “WRITE” and wait for the magic to happen… (This magic might take a few minutes)