How add a custom rom to android tv box

I recently bought an HK1 MaX tv box from ebay.
But it is a rooted device now I want to change it . And it’s not have beautiful UI, I want to change the rom something like "WebOS". I also like to flash windows But I think After I do that It will blow up "BOOOOOOOOM" 🔥🔥🔥🔥
Help me to do this . I don’t know how to change the rom. No matters if data loss .
Do I need pc for that ? Can I install a OS like BlissOS ?
Thank you