You will get the Mega Bracelet from Steven on Route 118 as part of the main story. This happens during a cutscene after you defeat Norman at the Petalburg City Gym, so the Mega Bracelet is an unmissable key item.
But before reaching this part of the story, you will first need to clear all prior gym leaders and beat Norman for the Balance Badge.
Getting the Mega Bracelet (Step-by-Step)
After you beat the Petalburg Gym you’ll obtain HM03 during a cutscene. Then Wally will take you to Mauville City right afterwards.
At that point, exit Mauville to the east to enter onto Route 118.
Step 1: Head east from Route 118’s entrance.
Step 2: Keep heading east, past the Aroma Lady trainer. Continue until you reach the beach area.
Step 3: On the beach, keep heading east until you reach the shore.
Step 4: Use Surf on the water at the shoreline and head east.
Step 5: Continue heading east on the water until you reach the shore on the other side.
Step 6: Get off the water on the eastern-side shore, and then head south on the beach.
Step 7: Follow the beach along until you reach the southern end, then turn to head east until you reach the end of the beach.
Step 8: Once you reach the end of the beach, turn up and head towards the grassy area above.
Step 9: You will immediately run into Steven here, starting a dialogue. The cutscene should proceed automatically from here.
Step 10: During the dialogue, Latios (AS) or Latias (OR) will appear.
Following the short cutscene, you will arrive at Southern Island.
Step 11: On Southern Island, head towards the north.
Step 12: Enter the clearing on the north side of the island.
Step 13: You will find Latias (AS) or Latios (OR) at the end of the clearing. Walk towards the Pokémon here.
Step 14: After a short dialogue, an evil team Admin will show up with a grunt and challenge you to a fight. Steven will join forces with you in a double battle.
- The evil team duo has a level 29 Koffing and a level 31 Sharpedo/Camerupt
- Steven has a level 35 Metang
Step 15: After you win the battle, the game proceeds automatically once again. Latias/Latios will then join your party.
Step 16: After you obtain the Legendary Pokémon, Steven will give you the Mega Bracelet.
Both Latias and Latios are already equipped with their respective Mega Stones.
And with the Mega Bracelet equipped, you will now be able to Mega Evolve other Pokémon in battle as well – assuming you already have their respective Mega Stones.