Ahead of a match, your team admin names a squad from the players available to that team. By default, up to 14 players can be named for a single matchday, split into 11 starters and 3 substitutes.
Once the squad's set, the same view shows the formation and starting line-up, including a visual pitch layout so it's easy to see who's playing where. If you're named, you'll be able to see your own position in the line-up alongside everyone else's.
Being available doesn't guarantee selection. Squad and line-up decisions are entirely down to your team admin's judgement.