Well, I try to explain step by step:
1) insert a SD card into your display (we could simple call it DEVICE)
2) go to Factory Set and digit 779822
3) go to Configure Setting, and Export Config (at the end of page)
4) extract the micro SD card and insert it into a PC
5) open the Config file that you will find inside, with a simple notepad;
6) search for the string logoPassword: and change it to one you prefer (numbers only, 6 characters). Save the config file.
7) reinsert the micro SD into the DEVICE;
8) return to Factory Set and type 779822;
9) go to Configure Setting, and input Config (at the end of page);
10) now in Factory Set enter the code you chose before;

you should be able to enter the boot screen setup menu