Hi:
Here is a pictorial step-by-step approach:
1. Select Tools > Import.
2. From the dialog box that appears, select 'Configure Auto-Import' and then 'Next >' (photo below: Importing Files 1).
3. From the next dialog box that appears, select YOUR folder that contains your 'mp3' and 'WAV' files. Then select 'Edit...' (photo below: Importing Files 2).
4. From the next dialog box that appears, from the 'Import these file types:', check (if not already checked) 'Audio' (photo below: Importing Files 3).
5. Then expand the option by clicking the delta icon, which is to the left of the check box.
6. Next, check the file types you DO want to import and uncheck the file types you DO NOT want to import (photo below: Importing Files 4).
7. Select OK when complete.
I hope this helps.
Cheers,
Lawrence