It is available in the README.
Run i.MX Linux Yocto Project Setup:
$: [MACHINE=<machine>] [DISTRO=fsl-imx-<backend>] source ./imx-setup-release.sh -b <build folder>
In my case I run:
MACHINE=imx8mmevk DISTRO=fsl-imx-xwayland source imx-setup-release.sh -b build/