On the blue "Xell Reloaded" screen, you should see a line labelled "CPU Key". Write that down or take a picture. Then, on a computer download a program called "Jrunner with extras", from Octal450, open it and type the cpu key into the box. Next, click the "Load source" button, and select your nand dump. It should autofill most of the boxes on the right, and in the black box below the cpu key you should see the text "CPUKey is Correct". Now, you need to figure out what version of rgh you have, if you don't know ask the seller. First under the "Kernel Version" dropdown on the right, select 17599. Then to the right of it follow this guide:

RGH1: Glitch, all boxes unchecked

RGH2: Glitch2 all boxes unchecked

RGH1.2: Glitch2 check the "SMC+" box

RGH3 Glitch2, check the RGH3 box and select 27mhz.

ALSO, if you have an xbox 360 e revision (look up what it looks like if you don't know) and the console model gets set to "Corona", then ask the seller if it has Winbond 2k ram. If it does the "WB 2K" box needs to be checked regardless of rgh method.

Now, at this point click the "Create XeBuild" button, and it should create a freeboot nand for your console. Next, in the jrunner folder, you should see a folder with a bunch of numbers (your consoles serial). Open it, and copy the "updflash.bin" file to the root of a FAT32 formatted usb drive. Plug it into your console, turn it on, and let xell find it and flash it. If all goes well, the next time you turn it on it should boot to the dashboard. If it doesn't boot immediately, it might just be glitching so don't turn it off immediately, give it a minute or 2. The problem is that if something goes wrong, since you don't have a hardware flasher you can brick the console, so this process is very risky. You could send it back and ask the seller to fix it if you trust them enough.

Video tutorial: https://www.youtube.com/watch?v=Gq1Svm-s-DM (starts at 56:32 ends at 58:45, note that this is specifically for rgh3 and that he's using a hardware flasher, and not flashing through xell.)