Plug uSD card (minimum 8 GB of size) in the host machine.
Flash petalinux-sdimage.wic.xz (locally built or downloaded prebuilt) in to the uSD card.
Install and launch Balena Etcher (or any image writing tool) and follow the wizard.
Browse and select the petalinux-sdimage.wic.xz image as file to be flashed. (Balena Etcher will uncompress the .xz file automatically. Uncompress manually, if other tool is used)
Select target as uSD card
Click flash to write the image.