Where a key chain organizer should be installed depends purely on your personal convenience and preference in terms of where you think the holder would look best. When you look at it purely from practicality stand point, it is always good to have them installed behind the entrance door or the foyer leading to the entrance. That way you will remember to put the keys in their place and remember to take it when you step out. If the hanging keys is an eye sore, you can see if there is a cabinet inside which you can have it installed. Either way, base your decision on the overall look of your space or the functionality.