Please go to http://www.phschool.com/home.html (or click on the link) to get to the Spanish textbook website.
At the blue menu bar, on the left of the screen, select World Languages.
Under Student Resources select Textbook Companion Sites.
On this screen choose Realidades textbook and on the next screen choose Level 1.
Now you will be on the home screen for the online book and you can find the chapter and activity you want to work with for that chapter.