We recommend allocating several minutes each day to sight reading practice.  A good way to use the book is to read straight through a piece in rhythm, as slowly as needed, perhaps repeating it once a little faster.  Then go right on to the next.  You can put a mark on the page every time you read a piece-once you have collected a certain number of marks on a piece do not read that piece any more-start your reading with the next one.  The number of marks depends on the age and experience of the player; most likely between 3 and 7 times.