How to write the eMMC after booting up the SD card

I am a noob.
I followed the guide and now I can boot up using my SD card but now I want to put the Ubuntu image into eMMC so that I don’t have to use the SD card to boot up. I might have to remove the android TV os that came out of the box but don’t know how.

-Rock960 model A

You should be able to write to it using ‘dd’.

sorry, what is dd. I am completely new to this. Also is the Ubuntu image on the official site a gui or terminal based

Have you looked at the following steps:

It explains how to flash your image(s) on the emmc with rkdeveloptool