As a Parent
Navigate to the You tab. Underneath your child's name, you'll see their team along with fields for number and position. Tap Add Number to fill in their jersey number and/or position.
If your child already has a number or position and you need to update it, simply tap their current number and you'll be given the option to make changes.
As a Player
In the You tab, scroll down to Your Teams and tap Add Number underneath the relevant team.
As an Admin
Admins can edit jersey numbers and positions for any team member. Go to Team > Members, then tap the three dots next to the player's name and select Edit Number and Position.
You can also use the position field to add more about your role in the team, for example "volunteer" or "team mom."