There are a few options when collecting this kind of information, but surveys would be the recommended route when requesting free text responses on a NationBuilder site. Plus, you can more readily view and export the nomination results from within your survey settings.

Alternatively, some customers use custom fields for this kind of functionality -- often so that users can answer all the questions on one page or create multiple choice checkboxes (both of which are limitations with survey pages). More on implementing custom fields:

Introduction to custom fields
How to create custom people fields
How to request custom people fields on webpages

You might also consider using an integration with a more customizable form generator, such as 123FormBuilder.