Access the online textbook from the publisher. Sra. Coburn will give you your access code. Create your account using your KHS user name and password. Once you are registered just go to PearsonSuccessNet.com and log in.
For the Realidades 3 text, most on-line activities start with the code letters jed followed by 4 digits. The textbook and workbook pages give the specific codes for the corresponding online activities.