Grimdark Future Rules

Grimdark Future is a game in the default, "battle" scale of combat. This means that the game is played with armies of a 1000 to 3000 points each. The armies consist of 5 to 15 units. Units are often composed of 3 to 10 models which can each move individually as long as they stay together. But larger units of 20 models, or units comprised of a single vehicle or monster are also present.

You can find all the official rules you need to get started here: OPR Games | Grimdark Future