how to unlock phone I got form a friend

I suggest you ask your friend for help, depending on the "lock" problem among these:

Unlock 1 = Apple ID locked (Generic):-> If your Apple ID is locked or disabled - Apple Support

Unlock 2 = Apple ID locked (in AppStore&iTunes):->  If you see a message that says 'Your account has been disabled in the App Store and iTunes'

Unlock 3 = Passcode forgotten:-> If you forgot the passcode on your iPhone, or your iPhone is disabled

Unlock 4 = SIM not supported:-> How to unlock your iPhone for use with a different carrier - Apple Support

Unlock 5 = SIM PIN:->  Contact your carrier asking them for your SIM PUK code

Unlock 6 = Activation Lock:-->  How to remove Activation Lock

Unlock 7 = Frozen device:--> If your iPhone, iPad, or iPod touch won't turn on or is frozen - Apple Support

If you mean something different, please better specify your needs.

Regards

Giulio

Your friend should have done this.....before....they gave you the phone.

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

If he/she can't do this now......the phone has been stolen and will be useless.