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.

How do you activate mega evolution?

Mega Evolution can only be activated when the trainer has a Key Stone and the Pokémon is holding its specific Mega Stone. Vaeryn will give the player the Mega Bracelet as their Key Stone and one free Mega Stone that matches one of their party Pokémon upon defeating him at the Snowbank Town Gym.

Can you permanently mega evolve in Pokemon go?

Mega Evolution in Pokemon is a temporary transformation of some Pokemon. This evolution can “boost” a Pokemon, meaning that they will have a different appearance, different base stats, and abilities from its regular-evolved form.