You must beat team rocket at Pokemon tower and the rocket hideout then get the 5th badge.
You have to go to Silph Co in Pokemon LeafGreen. You have to go there to get the Silph scope, which you need to advance.
In Silph Co. in Saffron city. After you get to the top of the building.
You get it form the owner of the Silph Co building after you save him.
On the 5th floor of silph co.
in saffron city big building
7th floor.
Saffron City.
You need to trade a Porygon holding an Upgrade.You get an Upgrade from Silph Co building.
you get it in silph co which is in saffron city. after the boss fight, the leader of silph co gives you one.
Get the silph scope at silph co in Saffron city. Then you'll be able to fight the ghosts.
Save Silph Co., Just like in Blue.
in the silph co. building.