It's all relatively simple. In short, you send the blank tape(s) to the librarian; the librarian dubs your selection and returns the tape(s).

Here are the steps:
1) Make your selection from the tape listings.
2) After ascertaining the tape length required for your selection, buy the tape.
3) Submit your request.
4) The librarian will acknowledge your properly submitted request by providing an Authorization.
5) On receiving your Authorization, promptly send the librarian the requisite tape(s) of the appropriate length and a self addressed mailer with return postage affixed (International patrons please see link to "Information For Patrons Abroad" below). Do not send money. Include a printout or copy of the authorization provided by the librarian.
6) The librarian will dub your tape(s) and mail it/them back in the postage paid mailer that you provided.
7) OPTIONAL! Do the same for someone else.

New Patron's Page
Information For Patrons Abroad (non US)
The Information Desk
The Unofficial Bob Dylan Free Tape Library Home Page