To configure your own fields, double tap first on any student in your grade book
You'll be presented with this screen
Tap on the Three dots button on lower right corner
This will let you add or remove your own personal fields grouped by a section. In our example, we will add two phone numbers (i.e. Phone 1 and Phone 2) and we will name our section Emergency.
And the resulting screen ,with our new fields will look like this
Show a selection of personal fields in the gradebook view
From the gradebook view, Options button (top right corner) and you will be able to show your own fields.
If there are many, you should increase the row's height in this very same view.