My phone was stolen so I remotely locked it and now I can't open it(I managed to recover it) as it says 'the phone you are using is lost or stolen' How can I unlock the phone again?
I'm assuming you locked the device through Android Device Manager. But yes you need to really edit your question to make it more understandable. Shut down is also not an appropriate term to mean locked.
- If you indeed used Android Device Manager to lock the device then you were requested to enter a password . You will use that password to unlock the phone.
- If you forgot that password then your other option would be to perform a hard reset on the phone. Again you haven't informed us of the phone model but most android variants require the phone to be off first then press the on key simultaneously with home key and volume down key. You will then boot into Recovery mode. Select wipe data/factory erase through navigating with your volume keys and selecting using the on key. Note this will erase everything on your phone on the internal storage.