If you have created a Student profile for a new student and have not yet allocated a UPN to the student, you are able to do this, by going to the Student Profile and their Extended tab. Scroll down to the School Information area:-
You are then able to use one of the following buttons, depending on what you wish to do:-
This will allocate a UPN for the student which then has to be saved by scrolling to the bottom of the page and clicking on the Save button.