It is not easy to write a tutorial if we don't know what is on the device...

telnet?
ssh?
terminal?
g_ether driver?
Is wifi working?

The first thing is I would try to use the rescue image if the flasher is able to upload it and if it is booting.

Then we need to find a way to transfer files, one way is to use the rescue image if everything is working. The easiest way would be the micro sd card.

Or at least we need to find a way to use telnet it is a dev device so I guess telnet or ssh should be installed.

If the rescue image is not working, we would need a terminal to investigate more the os on the device.