You can add up to 5 custom fields. They are included at the bottom of the petition email sent to your target.
Go to dashboard > SpeakOut! > petitions > edit > display petition options tab and click on of the Display custom field n checkboxes to reveal some option fields including the field label, placeholder text and whether or not to make it required.
Custom fields 1 – 4 are standard text fields.
Custom field 5 is a drop-down field. Options can be added in the dashboard values field by separating each value with a | character e.g. one|two|three|something|else