Apparently, you need to visit the swamp, but for Celica to have this staff and... body with her. Nel didn't hold some lessons for nothing.
Yes, English and Indonesian are noticeably different.
Anyway, the swamp is near the entrance to the elven enclave. Where the boring elf guard stands. Closer to the right border of the game's world map. Octopus-like monsters also appear there.
The staff's spell, like some other items, is activated if you left-click on them in your inventory (at right).
But in general. it will be more difficult for you to play further, since the game is based on the plot.