After you log in, tap on your avatar at top left of your screen. There, you will see a section with the blue title, "User Profile". Tap that. Tap in the fields to make entries. Remember to tap "Save" at top right when you're done.
While you are not required to enter Profile information, it is frequently helpful to your care team.
Your data is private, including private from your care team, if you choose to limit their viewing and/or editing permissions. You can choose to share as much or as little of your health data as you wish.