@borasavas Much like any tabletop RPG like Dungeons and Dragons, Pathfinder, Call of Cthulhu, or any others, to play you will need a copy of the rules, either the pregenerated character sheets or blank character sheets, several friends to play with, and either one of the premade missions or missions that you create yourself. The rulebook contains further details on how to go about running and playing the game.
@borasavas Thank you for your interest in the Open Beta of the Stargate RPG. The PDF file that you downloaded is everything that you need in order to play the beta version of this game as it includes the current rules, character creation guides, and other information to allow you to play the game as it currently stands. This is a Table-Top RPG and not a computer-based game.