Select More apps on the left side of Teams. Here you'll find:
Your personal apps. Any app you've added that offers a personal view or workspace.
Your team apps. Apps that have been added by your IT admin or a coworker for the teams you're in.
Custom apps you've uploaded. If you're a developer and have uploaded custom apps, you'll see all those here, too.
Whenever one of your team apps has something new to tell you, a red number shows up next to the app icon, letting you know how many notifications you have.
View apps for a particular team
Find the team name, then click More options > Manage team > Apps.
You'll see the apps added for your team, and you can delete and add apps from this screen, too!