You may find it's not only students that contact you via the Enquiries app. In this case, there is a tool for adding an enquirer's occupation directly from their enquiry.

Click the three dots on the Student Details card and hit "Edit". You can either select an exiting occupation or add a new one.

Please note that each new occupation is assigned to that enquirer. To add several new occupations you will need to find an enquirer that matches each occupation you wish to add.