if you make any pokemon faint, you can't catch it. sorry, but if you've made them faint, you only chance of having them in your possession is by trading with other people or by restarting the game.
to catch those pokemon, you first have to complete your sinnoh pokedex. to do that, you have to see (you don't have to catch) the 150 pokemon in sinnoh. after you've seen them all, professor oak will give you the national dex, and you'll be able to encounter and catch the rest of the pokemon, excluding legendaries and starters from other versions, like charmander, totodile, lugia, etc.
