After accepting your invitation to a Talk Story interview, within 24 hours, you should see a shared folder invitation from Dropbox in your email inbox. As an example, this is the email I received when I shared a folder from talkstory.interviewer to talkstory.interviewee.

After clicking on "Go to folder", you'll want to login to Dropbox. If you don't have an account with that email address, see Create a Dropbox account.

For more help, see the Dropbox document "How to add a shared folder to your account".