I'm not at a pc with CATIA so I can't be sure about what the exact steps are. I do know what you did, though. On the View toolbar there is an icon for changing the perspective. By default it is on Iso. If you click on it, you'll be able to see the other perspectives (Left, Right, Top, etc.). Anyway, once you click on it (and it is still active), you can change the perspective using the Up and Down arrow keys. You don't need the arrow keys to do this ... simply change the perspective with mouse selections. It is cool, though ...
Archangel