...

Regarding to get image file, there are three steps.

FirstFirstly, please select "Develop board".

SecondSecondly, please select "Rootfs".

ThirdThirdly, please select "Boot from".

...

Figure 5 shows the picture of Yocto Image Maker page after run finished. You can see the ISPBOOOT.BIN(emmc) the 2020-08-20-raspios-buster-armhf.img.bz2 word with blue color in the main window. Click ISPBOOOT.BIN Click 2020-08-20-raspios-buster-armhf.img.bz2 word to download the bin file.
 

Image Added

 
Figure 5.Yocto Image Maker page . Get 2020-08-20-raspios-buster-armhf.img.bz2 after run finished

2.2 How to get Yocto source file

...