Import Audio File…    ⇧⌘I

Add a new file to the project. I should experiment with deleting unused sections from audio files. I have lots of tracks that are less than 30% “populated”.

Add and delete audio files in Logic Pro — Apple Support

When you add an audio file to your project, Logic Pro automatically creates a region that encompasses the entire file length. You can create as many regions as you like from the same audio file. There are no length limitations to regions, as long as they don’t exceed the length of the source audio file. Creating multiple regions from the same audio file is beneficial for many tasks—using different portions of a vocal take that spans the length of the project, for example.

You can delete audio regions and audio files in the Project Audio Browser. In addition to deleting unused audio files, you can also delete unused portions of audio files. This usually frees up a lot of space on the hard disk.