i am unable to unlock my ipad

There's multiple kinds of "locking" on devices. Click on the links below to find instructions on how to deal with your specific situation:

1) iCloud: Activation Lock - http://support.apple.com/kb/PH13695 - This is a security feature so only legitimate (i.e., not stolen) redistribution of devices is possible. See: 'How to remove Activation Lock' --> https://support.apple.com/HT201441 - If an activation lock was put on a device, only the owner of the account that applied the lock can remove it. Get them to remove it or return the item for a refund. If you are the owner, see the part at the end about asking Apple to reset the device.

2) Device lock: "If you forgot the passcode for your iPhone, iPad, or iPod touch, or your device is disabled" click here --> https://support.apple.com/HT204306

If you're having problems then we need to know what you mean by "locked". Knowing the exact error message helps a lot.