In the Timeline, you will find all the actions that you've added in your video.
On the left side of the editor, click on Timeline to see all the apps that was added to your video. You will also see the time when the app will appear in your video.
Adding an app to your timeline
Click Timeline on the left panel. and hover your mouse over the video for the video timeline to appear
Click on the time where you want to add the app
Click APPS on the left panel and select the app you want to add
To change an app settings, click on Timeline on the left panel and click on the app you want to configure
You can also change the time stamp when an app will appear by selecting the app and dragging the app on the video timeline