Explore! Use what you learned with the first control panel to set the second one on your own.
You haven't used the fourth bolded phrase in Atrus's journal yet.
Use the tapestries on the lower level to find the symbols for Balanced Systems Stimulate Civilizations. While you're down there, you might want to pick up the Tomahna linking book, for future use. Go back upstairs to enter the symbols (avoid a common mistake - make sure you extend the upper curves of the Civilizations symbol halfway down the circle). Once you enter the symbols, it would be a good idea to save your game.