To include a checkbox field, click Convert > Landing Page. Then, select the Landing Page containing the form you want to edit. To edit your form, click inside the form box on your Landing Page and go to Edit fields, as shown in the image below:
The form appears as follows:
Select the field you want on the left side of the screen, under Fields. If you haven't yet created the desired field, click Fields > Create new field at the bottom of the screen.
The screen below will be displayed. Fill in the field name and placeholder as you wish. For field type, select Selection field - Verification checkbox and click Add:
The field will now be available under Fields and you must select it in order to be included in your form. In our example the form was set up as follows:
Click Save and continue. Don't forget to publish the Landing Page for the changes to take effect.