After importing audio flles you can create a project, which will have multiple tracks on a timeline on which you can arrange your individual audio files.

To do so click on the New Project icon:

Now, save the new project, by clicking at the top on File...Save As.

Save and name the project in the same folder where you imported your audio files (such as in the Source/Audio folders on your external firewire drive).

Notice the difference between the tabs for a project and for audio files at the top of the Project Window.

The sound files have a small wave file icon to the left of their names.

The multitrack project files look like stacked multiple tracks.

You can toggle between the individual audio files and your project, by clicking on the tabs.