How do you evolve a Pokémon in the TCG?

Match the printed evolution line

Read “Evolves from” on the card rather than relying only on a familiar species relationship. Put the Evolution card on the matching Pokémon, whether it is Active or Benched, when the timing rules allow it.

The Evolution becomes the card you use for its current attacks and Abilities unless a rule says otherwise. You do not ordinarily keep choosing attacks from every earlier stage underneath it.

Keep damage and attachments

Evolving does not normally heal existing damage. Damage counters and attached cards remain, while Special Conditions and other relevant effects are cleared under the evolution rules.

Because the new card can have different HP, the same damage counters may represent a different amount of remaining health. Check the new HP rather than removing damage just because the illustration changed.

Respect the waiting period

A Basic played this turn normally waits until a later turn to evolve. Evolving to Stage 1 does not normally permit immediately stacking Stage 2 on top in the same turn. A card effect can create an exception, but the exception must actually say so.

Neither player ordinarily evolves on their own first turn. Going second does not remove that limit merely because the opponent has already taken a turn.

Effects that skip stages are specific cards

Read the entire text of an evolution-support card, including which Pokémon and timing it permits. Do not summarize every such effect as permission to put any Stage 2 anywhere.

If an evolution is rejected in Live, inspect timing, the exact printed line and active restrictions before assuming a software error. Those same checks help resolve the question at a physical table.