How do you evolve eve without using a stone in firered?

You can't evolve Eevee into any of its evolutions without using an Evolution Stone in FireRed.

Here are the stones and their respective evolutions:

* Thunder Stone: Jolteon

* Water Stone: Vaporeon

* Fire Stone: Flareon

Eevee will not evolve naturally in FireRed, so you will always need an Evolution Stone to achieve its final form.