To use any of the stones in Pokemon Conquest, you have to equip the pokemon compatible with the stone, go into battle (preferably a training battle and not one to conquer a castle, but that's just me), if you win, you should get a scene of the pokemon's owner says something along the lines of "Something is happening to [insert pokemon here]," then the little evolution scene will happen. The only ones I've done are Thunder Stone for Eevee to Jolteon, Water Stone for second Eevee to Vaporeon, and Moon Stone for Jigglypuff to Wigglytuff.
use a thunder stone on pikachu.
thunderstone cave
Use a thunder stone
You'll need to use a Thunder Stone on a Elektrik.
You can get it in Cerulean but pikachu won't let you use it on him in yellow.
Equip the Warrior with the Stone and then in a battle or a training session, use it on that Pokemon. And voila.
Use a thunder stone on an eevee
use a thunder stone on pikachu.
thunderstone cave
Use a thunder stone
you have to use a thunder stone
use a thunder stone on eevee
On a pikachu to evolve to a raichu
Underground use the Explorer Kit.
in battle go to warrior and there should be a fire stone there and use it and after battle he should evolve
you use a fruckin thunder stone
You'll need to use a Thunder Stone on a Elektrik.