So..
Mount is the command for making DosBox set up a new volume
C is the drive-letter the new volume will have
C:\DOS\CDrive is the REAL directory on your harddrive you want to have the VIRTUAL C:\ to start in (so all the directory-tree in C:\DOS\CDrive will be under the EMULATED C:\ )
If this doesn't work, then there is something wrong on your side with your software/hardware
Simply typ this:
mount C C:\
C:
cd games
cd the_game_you_want_to_play_that_is_located_there
game.exe