You can sell pokeballs in auction house, but selling balls with captured pokemons is (not ethical) crashing game. But remember that pokemons can be aggresive (atacking when they see you), normal (atacking when you pick on them) or passive (runing away when atacked) - there's a list on home page. You can attack it by yourself or battle with your pokemon. How to catch a pokemon? First, lower it's HP (but don't kill it!). Each pokeball can be accessed by reaching certain level, and each have different catching rate. You can craft pokeballs in POKEMON STORE or in your personal Inventory.
The most successful way to catch your pokemons is using pokeballs (sth new?). The great treasure that POKEBALLs are Pokeball Did that? Now gather resources and craft yourself some pokeballs and summon your starters. Then you need to learn engrams of pokeballs (acces to ultra-, great- and masterballs will be unlocked by leveling up) and starter pokemons: Bulbasaur, Charmander, Squritle and Pikachu. So first thing u need to learn (engrams) and craft is POKEMON STORE. Wild pokemons can be tamed traditional way, but it takes very, very, very long. Built a base, gather resources, craft yourself a weapon and armor. When you first starting remember that rules are the same as in basic Ark. THE PAGE INCLUDES INFO ABOUT THE MOD, NOT BASICS OF THE ARK GAME