Q: How to activate iphone to unlocked it

You cannot. If you cannot remember the account, you are going to have to find a way to remember it. If you are the original purchaser of the device from Apple or an authorized Apple service provider, then bring the device and an original receipt to a physical Apple Store to request assistance.

You cannot use the device without iCloud or Apple ID.

If you forgot your Apple ID or password, you can reset it here:  http://iforgot.apple.com

Are you the original owner? If so try this:

If you forgot your Apple ID - Apple Support