Click on your name in the top right of the screen and select "Account Settings"

From the main menu, expand "Job" and click on "Job Approval" then click on the name of the form you want to edit

Remove existing fields by clicking on the subtract icon to the left of the field

Edit existing fields by clicking on the 3 dots to the right of the field and selecting "edit"

Add brand new fields by scrolling to the bottom of the form and clicking on the "New Field" button and then selecting either "Add from Scratch" to create a new field or "Pick from Library" to link an existing field