Creating admin options

I’m new to WordPress development and I’ve managed to create a top level menu in admin which when clicked displays a form with various fields. When the form is submitted it updates the database with the data entered into the fields, this part works fine. But what I want it to do, after it has saved the data, is display a list of all the data saved via the the form page.

At the moment it just displays the same form after submission. I’ve created another php file with the code to display the list but I don’t know how to get it to show.

What do I need to do to achieve this?