Shows insert sim when i insert sim screen goes black and nothing works

Are you using the same carrier SIM as the phone? If the phone isn't unlocked it won't allow use of a different carrier's SIM.

Are you orienting the SIM correctly? You can get the SIM in backwards in some phones, and in some cases with persistence, but look closely at the socket and you should see an icon that shows which way the cut corner should be (and the gold contact downward).

Do that with the phone off... once the SIM and battery and back are in place, then power it up.

Good luck!

:o)