i have iphone 6plus that from my friend spend me due to forgot user name and password what and how can unlock that iphone ?

Turn off Activation Lock --> https://support.apple.com/HT201441 - An activation lock can only be removed using the log-in information for the account that applied the lock.

If this is a device for which you are not the original owner, get the owner of the account to remove the lock or return the device for a refund. The device is otherwise useless to you.

Send your friend these links to try to recover it:

If you forgot your Apple ID [this is likely an email address you are using or used in the past] --> https://support.apple.com/HT201354

If you forgot your Apple ID password --> https://support.apple.com/HT201487

Without the ID and passcode you can not open the device.

You can't bypass Activation Lock without knowing the original Apple ID used with the phone. That's likely why your friend gifted it to you. I would recycle the device, it's useless to you, sorry.