The application supports importing all of the known polar diagram file formats. (If you have a polar file which will not import, please let Craig know about it.)
Sailing polar diagram files can be imported into LuckGrib in several ways.
There is a menu item in the File menu named Import Polar Diagram File… Use that menu item to import a polar diagram file. You can also open the Polar Diagram Manager and use its ability to import a polar file. The vessel settings editor has a menu which allows you to choose the performance settings for a vessel, that menu also allows you to import a polar file.a
Regardless of how you invoke polar file import, the import process is, of course, the same.
After importing the polar file into the system, it will be available through the vessel performance editors performance menu.