If you need to replace your voiceover, you can easily delete it and add a new one! Just click on the voiceover track to select it in the audio timeline. From there, you’ll see options to play or delete it in the menu that appears.
You can have up to 8 voiceovers saved in your project. If you get a notice that you have too many voiceovers, you can review and delete them from the Your Music tab on the left hand side of the Audio Library. The ones with a blue check mark are added to your project.