I recently got into watching the TV show Life (NBC), which the first season is available on Hulu. The day after Xmas I caught a nasty stomach bug that had me going at both ends, disgusting I know... Anyhoo, I got exceptionally bored over the next 3 days and I turned to Hulu for some episodes of House, which I can only manage to catch on Hulu for some reason (long story). I ran out of House so I started Life.
Simply put, after you create the multi-user account (assigning them a username and password) they can login in with that information into PayPal. The PayPal login box says E-Mail Address; just enter the username instead, and then the corresponding password.