How do i get the cloudy mirror recharged so it can open the chest at the arena and i think the thing on the wall that the person i guarding near the scar in the calm lands? (i already did the chocobo training and race)

Also how do i get to the optional bosses and the hidden/dark aeons that i hear people talking about?
I only have valefor, ifrit, shiva, ixion, bahamut, and yojimbo(sp?)

i also havent gone to fight sin at all yet incase that matters