Do I need a different membership per each gym I join?

Your Aaptiv member ID is the same for every gym you join. However, some facilities may give you a member ID specific to their gym upon enrolling.  That being said you DO need to enroll at each gym you choose to join in the Gym Network.  Be sure to look at  the Gym Notes on how to enroll, either by link or in person. You can find your membership number on the profile screen of the Aaptiv app.