You trade for it like anyone else
you can find one with a traner on 216
you must trad a porygon holding an up-grade
Porygon 2 can obtained by trading Porygon holding an UpGrade.
U have 2 trade him
there is porygon-2 but not porygon. porygon-2 is in oil field hideout
An Up-Grade is an item that evolves the Pokemon Porygon when Porygon is traded while holding it. Porygon evolves into Porygon 2.
You must evolve Porygon (From Celadon) using the UpGrade to Porygon 2.
porygon evolves into porygon 2
You give it to a Porygon and trade it, to get a Porygon 2.
That Would be Either Porygon or Porygon-2
It evolves Porygon 2 into Porygon-Z when you trade Porygon 2 while it is holding the Dubious Disc.
you give porygon the upgrade then trade it to get a porygon 2 then you give your porygon 2 another upgrade and trade yet again to get a porygon-z