How do u power up

ok i got moon sigil and crest...now how do i power up nirvana?

Go on the sparkly path in Macalania. Go to the big crystal and power it up TWICE.

Make sure you had done that sidequest with the lost father and kid, that's the only way to get access to the plant in Macalania Woods.

I think hes already done that. He got the Nirvana so he has to have the Celestial Mirror.