Articuno's Location

• 1). Fly to Fuchsia City and head south until you reach water. Use the HM Surf to reach continue head south until you reach the Seafoam Islands.
  
  
• 2). Enter the Seafoam Islands and navigate your way to the rooms with boulders.
  
  
• 3). Use the HM Strength to push all the boulders down the holes.
  
  
• 4). Fall down the holes by walking over them until you reach the third basement floor. Head north until you see Articuno standing on a ledge with stairs. Go up the stairs to reach him.
  
  

Zapdos' Location

• 1). Fly to Cerulean City and head east until you see an entrance to Rock Tunnel.
  
  
• 2). Head south until you reach water and use the HM Surf. Continue heading south until you see an entrance to the Power Plant to the east.
  
  
• 3). Enter the Power Plant and go to the northwest corner. You will see Zapdos standing next to a generator.
  
  

Moltres' Location

• 1). Fly to Viridian City and travel west onto Route 22.
  
  
• 2). Continue on Route 22 and defeat the guards in a Pokemon battle, then head north to enter Victory Road.
  
  
• 3). Push the boulders onto the circular switches using the HM Strength to lower the ledges that block your path. Head northwest and go up the ladder.
  
  
• 4). Head east and go up the ladder north the the ledge. Then head northwest and go up the ladder in the corner. You will see Moltres standing in the next room.
  
  

Capturing the Legendary Birds

• 1). Approach the birds and press the "A" button to engage them in battle.
  
  
• 2). Use your Pokemon to attack the birds until their health is very low. The birds are easier to catch when they have low health.
  
  
• 3). Use Poke Balls from the item menu to capture the birds. This may take several attempts as they can break free from the Poke Balls you throw at them.