External HD and Rekordbox Software

Hi - I've got into a bit of a mess - I was thinking that my Lacie 2T Thunderbolt Drive could do with a tidy up  so I copied the complete drive (all my music files) to a large internal drive on another Mac Computer - I then Erased my External Drive and copied the music files back on again - connected it to my Rekordbox computer opened Rekordbox and made sure in the TAB "Database" that the "Select a Drive" is set to the Lacie  -  unsure what to do next to import files(songs) to Rekordbox 

 

can you assist please