Create a Dropdown list

It sounds like you are trying to set up a form for your users to fill out on the frontend. If that is the case, you should take a look at the acf_form() function. You will still have to create your dropdown and populate it manually, but getting it on the frontend is another story.

If you are looking to auto-populate your field with the distributors, take a look at the “Creating a new field” documentation. Elliot provides a template for creating a new field which you can then populate using PHP.