When you add a music file, it gets added to the project along the timeline at the bottom of the screen.
You can trim the music file to adjust the duration by clicking on the end of the music block and dragging it, as shown in the video below.
You can also manually drag the music file along the timeline to position the music file as per the requirement of the project.
To know more about Speechify AI Studio, you can browse our AI Studio tutorial videos in the Speechify Studio Academy.