Where do you use the mystic ticket in Pokemon FireRed?

You use the Mystic Ticket in Pokemon FireRed to access the Safari Zone.

Here's the breakdown:

1. Obtain the Mystic Ticket: You receive the Mystic Ticket from Mr. Fuji at Cinnabar Island after defeating the Elite Four and becoming the Pokemon League Champion.

2. Travel to the Safari Zone: Head to Fuchsia City and use the Mystic Ticket at the entrance to the Safari Zone. This will allow you to enter the Safari Zone and catch Pokemon within its boundaries.

The Safari Zone is a unique location in Pokemon FireRed with its own rules and mechanics, making it a worthwhile experience to explore.