My phone is locked how to unlock it

How exactly your phone is locked?

If your iPhone is locked by a carrier, you need to contact this carrier to unlock it. Note that this is only possible when the contract has been already terminated and there're no charges left to be paid.

If your phone is disabled, take a look at this Apple Support article:

If you forgot the passcode for your iPhone, iPad, or iPod touch, or your device is disabled - Apple Support

If the phone is locked with the Activation Lock, you need to contact the seller and ask him to remove this iPhone from his list of devices. Otherwise, your iPhone will be a useless brick.

Find My iPhone Activation Lock: Removing a device from a previous owner’s account - Apple Support

Unlock your phone from what?

Stupid question, so provide more details if yo want help!!