*confused* about celestial weapons....

I am so horribly confused... someone please help me!! I have the Mercury crest and the mercury sigil and the celestial mirror and the godhand... but I have no clue how to upgrade it from being the crappy "no ap 3 extra slots uncostumizable thing that it is"

Go back to the thing that turned the Cloudy Mirror into the Celestial Mirror in Malcalania Woods and um talk to it.... That should do it! :D Your welcome!