the leaf stone

Use the stone on a Pokemon that can evolve with it. These are: gloom into vileplume, weepinbell into victreebell, exeggcute into executor(i spelled those last 2 wrong), and nuzleaf into shiftry.

First have it on your "items section", one common mistake about using stones is that the stone is given to the Pokemon, this is completely wrong. Instead select USE and select the Pokemon you want to evolve. Remember that only specific Pokemon can evolve with the leaf stone. Those Pokemon are:
-gloom -weepinbell -exeggcute -nuzleaf
Once you use any evolution stone, the stone disappears so use it wisely.

What they said me ib used mine on the nuzleaf

All you do is go to items and select leaf stone and when it comes up on your party pokemon. select a pokemon that can evolve when using it. it is that simple not all pokemon can evolve from the leaf stone i used mine on my nuzleaf

you click on the stone you want to use then pick the pokemon you want to use it on then it should evolve

well if you have a pokemon that needs a leaf stone to evolve then use the stone on the pokemon and if it is his time to evolve he will.

All you have to do is give it to the Pokemon you want to use it on.