You can do a search of the forum. That question has been answered a few times
PhotoRead the entire textbook.
Do one 30 minute Activation of the whole book
Treat each chapter of a textbook as a book itself.
When activating specific chapters begin by PhotoReading the chapter. Include the 2 chapters before and 2 chapters after the chapter you plan to activate (it helps the mind to integrate the knowledge.)
Activate until it's gelled.
Use any questiosn provided in the book to help with activation and be sure to add more questions of your own.
As always know your purpose. What do you want from the book (chapter)
Alex