After class, take your physical book and open it while looking at the website you want to use. Find the appropriate page or lesson where the student or tutor should get online, and… *GASP* write the website in the book! Librarians, close your eyes.
If you have folks less computer literate, try typing up detailed directions about how to access the website & what to do when they get there. Make sure to type in your document what page in the book to stick the note in after you print it out. Staple the note to the book if you have to! Trust me, your students & tutors will thank you for the written reminders.