Activation lock

Hello all,

I've recently boght an iPad and it has an iCloud. Since I wasn't very familiar with all the Apple products, I've tried to remove the current iCloud so I can add my own.

Since I didnt have a password for that account I've reset the ipad, and I was thinking that now I will be able to add my own id. But now I cant even acces the ipad, I got the activation lock. I know the email of the current id ( previous owner) but I dont know the password.

How can I access my ipad, also I know the serial number.

Thanks