Ipad I just bought

You will need the assistance of the previous owner. If you can't contact the previous owner, try to get a refund if you bought it through some place that has buyer protection (such as ebay).

Also see: Activation Lock for iPhone, iPad, and iPod touch - Apple Support and How to remove Activation Lock - Apple Support

You require the assistance of the original owner or the iPad will remain useless forever.

Perhaps you purchased a previously stolen iPad. Get a refund if possible.

How to remove Activation Lock - Apple Support