Club fixtures looking for players
Clubs can mark a fixture as "searching for players". Those fixtures appear in the Find section. Browse by location, date and sport, apply to play, and if you're picked you'll get a notification and the fixture will show in your schedule.
One-off games
The Find → Games tab lists casual one-off games that need players—not always tied to a club fixture. Browse, apply and get selected the same way. Handy when someone posts a friendly or fill-in match and you want to get a game without joining a new club.