To find out if your device is locked, borrow a SIM card from a friend on a different network to you. Put the SIM in your device and try to make a call - if you can, your device is unlocked.
To get your device unlocked, get in touch with the network your device is locked to. They'll be able to unlock your device for you, though they may ask you to pay a fee before they do so.
We don't unlock devices or recommend getting your device unlocked in any other way because this can invalidate your device's warranty.