Your quorum is three (2.5 actually but try working that out without bloodshed).
Your last AGM presumably set the membership at five so your quorum is half that.
You need three memebrs to be at the meeting in person (proxies won’t count unless they’re approved by the meeting … which has to be quorate) and then you elect a new member who joins until the next AGM. The new member is elected by a simple majority of the EC members.