Steven Zahm@ Toni
Right now they do not work together. They serve two distinct purposes purposes. Form is to allow site visitor [unregistered users] to submit an entry for moderation for the directory. So only at minimum, only a name is required.
If you intent is to allow users to maintain their own entry, then that is the purpose of Link. Link requires a WP User account because it relies on WordPress login authentication. Link does not just Link an existing direct entry to a WP user, the user if they do not have a directory entry can also use the edit page to submit an entry.
The link to the edit entry screen for Link can be found in the upper right menu item in the menu bar. You can copy/paste that link and put it in a page if you want, be default, WordPress will show the login page before taking the user to the page. You could also use one of the may user login plugins if you want.
I hope that helps.