With something called CHEATS.
you see all the Pokemon in platinum and trade from your other games like emerald, blue, fire red etc and that is how you find all Pokemon in platinum.
There are 18 Fire Attacks in Pokemon Diamond, Pearl and Platinum.
There is no way of getting a Charizard in Pokemon Diamond, Pearl or Platinum. You can transfer a Charmander from Fire Red to your copy of Pokemon Diamond, Pearl or Platinum. A Charmander, Charmillion and Charizard can all be found in Pokemon Heartgold and Soulsilver as a wild pokemon.
migrate it from Pokemon fire red version
use a fire Pokemon
fire-type pokemon.
no Pokemon evolves with a fire stone in Pokemon platinum except eevee which turns in to flareon
fire dah
buy the Pokemon platinum book
for 2-5 turns
the three starter Pokemon are the same in platinum as diamond and pearl. They are chimchar-fire, piplup-water, and turtwig-grass.
fire punch isn't a TM in platinum. There is a move tutor who will teach it to your Pokemon. it is the tutor on the route west of pastoria city