Select the users that will access this application profile. If you don't select any users, this profile will not be available from the Web interface.
These are the options you will find under the 'Permissions' tab:
If you want a user or a user group to access more than one application, you need to create more profiles and then add this user to each profile.
The authenticated user will be able to choose from the Web interface which application s/he will connect to.