Android TV - how do I wipe and install everything from new?

[enginerev]

I have an Android TV box.
It's a Chinese box (they're all unbranded Chinese boxes right?)
I wanted to practice wiping everything and installing everything from fresh.
How do I do this? Where do I start?
Any pointers would be great.

2 things:

I want to backup as an image first. Just incase I screw something up horribly, I want to be able to just restore an image.

I want to install Linux and mess around. Installing Linux I assume will partition the drive? If so, how do I wipe the partitioning and reinstall everything?

Thanks.