how to unlock my iphone 6S

it needs a computer with itunes installed, it need not be your own computer, any computer would do, friends, relativs, computer store computer, public libarey computer, work computer

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

then DFU mode to Restore - Apple Community

if that does not help then it will likely require service at apple

unlocking what?

sim card pin code?

passcode ?

sim lock to carrier?

activation lock ?