can't figour out how to get it what do i have to do and where do i have to go

"- E. Kimahri's Spirit Lance -

Weapon Location: At Thunder Plains, pray by pressing [square] at any 3 glowing Qactuar stones, then return to the south part of the plain and follow the Qactuar ghost to a wrecked tower. It's on the right side of the screen, embedded in the rock wall, equidistant from the north and south boundries of the plain. Pray there. Although you can find the chest during your first visit to Thunder Plains, you cannot open it until you have the Celestial Mirror."

- gamefaqs.com