You can cover the whole duration of your project by having the same song repeated or by adding a different one. You can do so by following these simple steps:
- Open your project and tap on the Soundtrack section (right under the media preview at the top of the screen).
- Tap on the green plus button at the bottom of the screen and select one of the soundtracks you'd like to add to the project.
- After selecting it, it will appear right under the timeline as a green bar that will cover only the segment of the project that matches its length.
At this point, you can repeat this process to add the very same song or other soundtracks. They will all appear under the previous one as two separate green bars. To make sure they match the right portions of your project, long-press on each of them and move your finger to the right or to the left. Then, you can trim and adjust their duration by using the side handles of each soundtrack.