The Range can be used both before and after a workout, or any other activity that you enjoy doing. However, if you only had to pick one or the other, we'd encourage you to use the Range before a workout.
Using the Range Before a Workout
Releasing tension in your neck, chest, and traps before you work out can help you improve the range of motion of your shoulders along with the alignment of your head and neck, both of which can help you feel better during your workout. This can have the effect of allowing you to strengthen and stabilize around this better posture, leading to longer-lasting improvement in your pain. Many users of the Range have also reported feeling an increase in performance during their workout when releasing their tight muscles beforehand.
Using the Range After a Workout
Similarly, the Range can also be used as part of a workout recovery routine after you exercise. This may prevent the neck, chest, and traps from tightening up, as these muscles may be used a lot in any given activity. Helping these muscles relax and recover after your workout (or later in the same day that you worked out) may help you feel strong and keep your muscles happier more consistently day after day.
Be Proactive, Not Reactive
Ultimately, the Range can be used in more of a preventative way pre-workout to help get your body into better alignment. As it relates to using the tool post-workout, ideally it would be used to help with recovery (in a good way) following a tough workout, and not as something to "undo" the pain that was caused by pushing through a workout while your neck and shoulders were tight and/or out of alignment.