AppleID

You will need to contact that "someone" to properly remove their Apple ID from this iPad. If you are not able to get a hold of them, or they refuse to help, then you will not be able to get this iPad unlocked. No one here, nor Apple can assist with this.

If you can get a hold of them, have them follow the steps in this support article:

• What to do before you sell, give away, or trade in your iPhone, iPad, or iPod Touch - Apple Support

You have experienced Activation Lock. You need to get the person that you bought it from to unlock it and remove the Apple ID. If they cannot or will not, then you will not be able to get into it. If that is the case, return it for a refund if possible.