You are able to update your availability that is shown on your profile anytime. All you have to do is log into your account here- http://fitnesstrainer.com/signin and you can adjust your availability under the "More" tab. Your availability is not real time and does not update on your profile based on what you have scheduled with your FitnessTrainer clients.
If you have very specific availability for specific locations that you would like prospective clients to know, you can detail it in your "About Me" section of your dashboard.