The process began when I got Argos' piece of the Map. I recognized the symbols on the bottom. Later, when I was playing Wizard101, in the District of the Stars in Celestia, I saw THE EXACT SAME SYMBOLS. They were under the Celestian Zodiac pictures in the Archives! I went to the Wizard101 wiki and looked up the zodiac books and matched each one to one of the pictures, slowly decoding Celestian. After learning the symbols, I returned to Argos' piece of the Map, and, (with the help of a magnifier), decoded the message.
"East to the blue sun. When the stars align, the moon is key." What does it mean?!?