You will get the best use and enjoyment of the photobooth by placing it where it is easily seen and accessible by your guests.
You can also help your guests take full advantage of the photobooth by letting them know where the booth is located and that it is available at no cost to them. Also, let them know that they can come back and take as many photo sessions as they want. Better yet, explicitly tell your guests that they must visit the photobooth at least 3 times!