DOS Games Discussion

Hi all! I have Their Finest Hours: The Battle of Britain working in DOSbox (techinally DOSbox-Pure), but I'm unsure of how to install the add-on missions "Their Finest Missions" or how to access them in the game. I'ts been forever since I played it back in the day, so I don't remember. Has anyone managed to add these on successfully?

I've never played it, but the Amiga version seems to have some installation instructions at HOL.
(More or less just copy files from floppy to the HD game directory)