musescore 3 Mac installation

I have installed Musescore 3 on my mac book air and have been trying to open it for about 2 days now. It keeps popping up with:
"MuseScore 3" can't be opened because Apple cannot check it for malicious software. This software needs to be updated. Contact the developer for more information.
What do I do so that I can open the app and do my music homework??????