When you need to create custom student fields you can navigate to the settings on the menu bar and find the students on top.
Menu Bar >> Settings >> Students
When you enter the Student fields section you will find some default system fields. You can turn off the usage of some of these fields or add more. You can also create custom Categories and add fields to them.
When you add a new category you will get a popup page where you will need to add details like-
and submit.
After you have added a category you can start editing or adding new values of the fields in it.
Click '+Add New Field'
In this area add:
Click Submit to save.