To Mega Evolve your Pokémon, you’ll have to collect Mega Energy for that specific Pokémon. Find Mega Pokémon in Mega Raids, take them on, and earn Mega Energy for that specific Pokémon. The faster you beat them, the more Mega Energy you’ll be rewarded.
It will take multiple raids of the same Pokémon before you’ll have enough energy to Mega Evolve, and most Mega Evolutions rotate in and out of raids. Not all Mega Evolutions will be available year-round, so make sure to stock up on any Mega Energy you want before the Pokémon leaves Mega Raids.
Note that you can only have one Mega Pokémon at a time. If you Mega Evolve a different one, your first Pokémon will revert back to normal and you’ll need to collect Mega Energy to evolve it again.
Using a Mega Pokémon in a raid gives other Pokémon an attack boost, with an additional attack boost given to Pokémon of the same type. These boosts do not stack.
So far, only these Pokémon can be Mega-evolved:
- Venusaur (200 Venusaur Mega Energy)
- Charizard (200 Charizard Mega Energy)
- Blastoise (200 Blastoise Mega Energy)
- Beedrill (100 Beedrill Mega Energy)
- Gengar (200 Gengar Mega Energy)
- Houndoom (200 Houndoom Mega Energy)
- Pidgeot (100 Pidgeot Mega Energy)
- Abomasnow (200 Abomasnow Mega Energy)
- Amphardos (200 Amphardos Mega Energy)
- Gyarados (200 Gyarados Mega Energy)
Tons of other Pokémon will be able to Mega Evolve, though you’ll need to wait for Pokémon Go to add that specific monster’s mega evolution to the game. If you want to get ahead of the curve, make sure to start collecting high IV versions of these now before they release.