Not sure of that exact model, but any custom ROM would require unlocking the bootloader first. Try the steps on this page first to see if you're even able to unlock the bootloader.
I don't know if that's the same model or not, but the instructions are pretty generic. If the bootloader won't unlock, you're probably out of luck and will just have to debloat/tweak the stock OS as best you can. It may also require a code from the manufacturer to properly unlock. Sometimes they'll give those out (or more often, provide a webpage where you can request them), sometimes they won't.
If you can post the model number (usually can get from Settings -> About Phone) it might help.
That image does seem like just a stock image to depict a smartphone. Can’t hurt to try stuff at this point so thank you for info and I’ll post if I’m successful.