To add the app to teams, it replies on two main factors:
1. You have enough access right, if you want to find the app name in teams, like @CU10061430-0 mentioned.
You can find any app and add it to teams. ( you should avoid using this , unless you have one app which will be used for all users).
2. You are an owner of one environment, after you create app, you share the app to Team, normally you add it to a channel, which you have the access right.
Before you assign to channel ( you can ignore it), you are the ones can open it/use it. ( others who have more access than you can get it).
normally you add this by select the app in https://make.powerapps.com, Apps, select the app, and choose Share on the tope command menu, choose Add to Teams, then you follow the guide, after that you will see (find)you app .
Do you have Teams Administrator Role? This may be preventing you from installing the app into teams.
Under review
Thank you for your reply! To ensure a great experience for everyone, your content is awaiting approval by our Community Managers. Please check back later.