In Catfish, Store Administrators can display up to 3 custom fields based on their needs on customer signup form.
In order to achieve this task, follow these steps:
1) log-in into your storefront using your Storefront Administrator, then go to Configuration > Settings > Customer Settings.
2) Scroll down to the bottom of the page where "Display Custom fields" are. Depending on your need you can check all three extra fields.
3) To change the name of the fields, go to Configuration > Languages > click on View string resources
4) Click on the filter which is located in Value table and search for the exact value as well as exact filter as you see below:
5) Now you can change the value of each field as you wish.