Add description to the Attachments field for "Submit a request" form

At the bottom of our "Submit a request" form in our Help Center is an automatic upload form for adding attachments. I would like to add a description similar to the description I've added to my other fields. The problem is, the Attachments field is not accessible in our Ticket Fields Admin Settings so I'm not able to add a description yet I am able to add one to all the other fields (i.e. Subject, etc). Below is an example showing our "Submit a request" form for context.

I looked at the HTML for our Help Center and found there is a template called "New Request Page" with a reference to "{{request_form}}" but I'm not sure how to access that or edit it.