To evolve Porygon to Porygon2, players need the Up-Grade item and 50 Porygon Candy. The latter can be obtained by capturing and releasing Porygon, but the former will be a bit more difficult to find. The Up-Grade item can be obtained simply by spinning PokeStops, but it is somewhat rare.

How do you evolve Porygon?

Porygon (Japanese: ポリゴン Porygon) is a Normal-type Pokémon introduced in Generation I. It evolves into Porygon2 when traded while holding an Upgrade, which evolves into Porygon-Z when traded while holding a Dubious Disc.

Where do I get Porygon upgrade?

The Upgrade item can be found in the small passageway between the cliff and the large rock. Once you have the item, go into your Bag and give the Upgrade to Porygon so that it holds the item. With that set, you'll need to find someone you can trade it with, hopefully someone trustworthy.