You won't be able to save a meeting until you have Meeting Types set in the system. We usually set your system up with pre-set standards, but your school or MAT may have chosen to override this.
To customise your meeting types, go to Administration>Meeting Types. You should make your titles general rather than specific ('Behaviour Review', not 'Meeting with George's Mum Regarding Behaviour') because in the future you'll be able see these meeting formats in your data. The clearer it is what kinds of meeting you're holding, the more you'll be able to track and evidence your practice.