The reflector ("sail") will make sort of a bowl shape when you pull it and put the tab into the slot.
After that, you'll need some batteries and flashbulbs. For the exposure calculation, you'll need the guide number which depends on the particular bulb you use (generally printed on the box of bulbs).
You'll also need a camera that can sync with flashbulbs. It may be easier to use it as decoration.
Lots of companies made variations of these, and they are pretty common in antique shops and random collections of photographic "stuff".