Adding a Power Apps to a Teams is a very straightforward task. We only need to select the App to be added and then click on the Add to Teams option. After this action, a side panel will open with additional information to consider before actually add the App to Teams.
Then, the process continues opening the Teams desktop/web client to add the App to Teams following the standard process:
We can also add a Power App to Teams by using the Add to Teams option available in the App contextual menu: