You install another OS. It's complicated and I defer to XDA Forums on what you need and the steps required. Frankly I wouldn't bother today since games would run poorly if at all on those old tablets.
See what you can sell it for then shop the cheep tablets.
Hi my name is John,
I have a B&N nook tablet or color not sure which one. anyway I cant download any games or apps sadly because of B&N software. Can somebody please help me find a way to get rid of the software and install something like android on it. please. thank you.