If you have gotten yourself into the building using the disguise you can get in the underground, you should just make your way to the top of the building, afterwords you will get two different keys. One opens a door that leads to the Dept. Store where the president is and the second opens a door in the underground. If you have trouble defeating the trainers, I suggest using a Psychic Type Pokemon since Team Rocket mostly uses Poison Type Pokemon.
Beat the boss
you have to beat team rocket in goldenrod city
How do you get to goldenrod city in pokemon silver?
After beating team rocket at there warehouse and the radio tower at goldenrod city the director of the radio tower in goldenrod city will give the silver wing to you.
radio tower
After you beat them in mahogany town.
You need to defeat Team Rocket in Goldenrod City.
You have to beat the team rocket warehouse in goldenrod, and a guy gives you a silver wing at the end.
Easy! Goldenrod Tunnel, in the north west of Goldenrod City.
He is in Goldenrod City.
Team Rocket will be at the Goldenrod Radio Station after you have defeated Pryce in Magohany Town.
walk
Goldenrod city gym