To import an existing photo collection from F-Spot:
Select File ▸ Import From F-Spot.
Now choose either the default F-Spot library or another F-Spot database. If importing from another F-Spot database, select a directory and file from the chooser dialog box.
Shotwell will import your photos, together with their tags and other information. Once the import is complete, you can select Last Import in the sidebar to see all photos successfully imported. The Events list will also show new entries for the dates corresponding to the imported photos.