When you create a survey, you must check mark the Person Information that you want to be visible to canvassers when they are conducting Surveys during a Canvassing Effort. Note that the information must also be included in your original data set in order to be visible in the mobile app.
You also have the option to allow canvassers to add a new person, and you can check mark the fields that you would like canvassers to collect on people they encounter in the field. You can select the elements for each contact below the Person Information section and use the toggle buttons on the right to make them required fields.