^That is good advice. However, I think the question may refer to a screen lock with a forgotten pattern/password. If that's the case, you will have to google for your model and "recovery" or "reset" and similar terms. You will probably have to hold the Volume Up button while you press the power button to get into recovery mode, where you can restore it to the way it came out of the factory, erasing ALL of your data and apps and settings.