Monthly members just need to head to the 'My Gym' section of your Member's Area and follow the simple instructions. When you choose a secondary gym, you will also gain access to gyms that are the same price as that gym.
The price of your membership after the change will depend on which gyms you add to your membership. There will also be an extra amount added to your next bill to cover the price difference between your new and old membership. Don't worry - the exact amounts will be confirmed in an e-mail straight away you've made the change!