Import from Calibre
To import your books from Calibre open menu File -> Import From -> Calibre. The import window will be opened.
Press the Browse button and find the Calibre database file. Usually it's located in the Calibre library folder and called metadata.db
Press the Load button. This will load books from Calibre.
Select needed books (or select all - Ctrl+A) and press Save or Save All. This will import your books to Alfa with all metadata.