Second hand iPad
How do I connect an iPad to my iTunes account if I purchased it at a second hand store and the previous owner still has it connected to their iCloud?
You cannot. Take it back and get a refund. The previous owner or someone who knows the previous owner's iCloud ID and password are the only ones who can remove the Activation Lock:
Turn off Find My iPhone Activation Lock - Apple Support
Get your money back. You've been sold a brick....
Sorry,
GB