Zelda MIssing Character Help (Gerudo Area)

I am stuck and cannot figure out how to get by this area. I am right before the city in the sky, looking for the missing characters in the book and I need to find the missing character (letter) in the gerudo desert. I cannot figure out how to get there. The walkthroughs say warp to gerudo mesa or something like that but my only warp point in the gerudo desert is in the mirror place ( at the end of the arbitor grounds boss)

PLEASE HELP !!!

You realize you can use the cannon again?Shirley_Temple

k thanx thaqt should help