After freeing everyone in phenac you need to go to the mayor and he gives you an xp share as reward.
go to mr stone
In the Big building to the right of fuchsia city.
In Castelia city.. Is in one of the buildings last floor
how to get exp.share in pokemon blue
You can find the Exp. Share in Rustboro City or in the Lilycove Dept. Store.
If you give a Pokemon not in battle an Expshare, the half of the experience points will go to that Pokemon. If you're in a double battle, and one of the Pokemon in battle has an Expshare, 3/4 of the experience points will go to it. It's a very useful item for training weak Pokemon.
u find it in icius city (where the ice gym is) in the house south of the gym aka the Pokemon fan club
go to the bike path at eterna city
first go to Mr. Pokemon first have the red scale and he will give you it
You can get an Exp. Share from the chairman at the Pokemon Fan Club in Iccirus City.
you can only find shadow Pokemon in Pokemon xd
Simple, Give it to one of your weak Pokemon that you want it to be strong.