When exactly to drink protein powder can be different for everyone. Essentially, the best place for your protein powder is really where you think it could best fit your diet and lifestyle.
As a good rule of thumb, if you aren't before or eating after your workouts, we would suggest to include it there. It's great to help with muscle recovery post-exercise. However while it's the most popular time for it, you don't necessarily have to drink it at that time. Otherwise or on days you don't workout, try it as a snack, part of a meal, for dessert, before bed, etc. The good news is that you should consume protein sources throughout your day, so wherever you decide to include it will be helping your meet your protein needs.