PRESTASHOP 1.7 - Add two Custom Fields on a Marketplace Module

It is a prestashop 1.7 site with Multi vendor Marketplace Builder Module (https://prestahero.com/173-marketplace-creation) After signing in to my website with the normal registration the customers need to Apply to be a Seller which triggers this marketplace module and shows a registration form. I want to add two attachment fields on this form which should then be stored on the database like the other fields