Your display name is what your client will see when they view your profile or any other refernce to their trainer on the app.
To change your display name, start off by clicking the More button in the bottom right-hand corner of your screen. (See image below.)
Find the category that is labeled Profile in the menu options. (See image below.)
Below the Update Photo, you will see a the Display Name category. Click on this category and change it to your preferred display name. After you have successfully changed it, your data will automatically save. You are all set!