Start Here
The exercises are broken down into groups targeting specific note types. These build upon each other, starting with simpler patterns and progressing to more complicated patterns. Some sections include a consolidation exercise to bring together some of the previous patterns and combine them into new combinations. These will be more difficult and more like site reading exercises.
Introduction to Reading Music
If you've never read sheet music before, I suggest starting with Introduction to Reading Music. It will introduce the structure of written music and prepare you for the first practice session with quarter notes.
Dive into the Practice Sessions
If you're already confortable with reading music for the drums, start with the Quarter Note Reading exercise.