There are 2 ways you can add guidelines to an exercise.
One pretty obvious way is to write your guidelines down right before you send out an exercise, in the space provided specifically for that in this screen:
The other way, which is the one we clearly recommend, is for you to enunciate your guidelines such as the amount of reps, the technique, and the frequency as you're filming the exercise. This will make the process much quicker for you.
In other words, enunciate your guidelines when you see this screen: