Why do I need the Tomb Raider LevelManager?
To tell the truth: You don't need it at all!
Because if you like to mess around with about 10, 20, ...and even 100 or more files for each level, if you like to save the files of other levels to a secure place by yourself, manage your savegames and screenshots without any help and compile all the levels by your very own the LevelManager is a really awful and unnecessary tool.
But in any other case and for all the other people the LevelManager is built to be the perfect tool to archiv your level files, install them, and handle them.
So the only thing for you to do is to select the level you like to play and press the "Play" button then...

So, get your keyboard ready, get your mouse ready, get your fingers ready and look: This babe is really hot to jump up n down, out of a train and get into dirt for you...