You also have the option of changing how things decay-like structures, food, dinosaurs, etc. If you want to spice things up, though, you can actually change all of the rules of the game, including damage output, the overall difficulty, and even the rate at which you tame dinosaurs and gain experience.
If you just want basic settings, with the default setup, then all you need to do is launch the game, press the Host\Local option, and then choose Play Single Player from the center menu. Launching into a single player game in Ark is very easy, but it also comes with a lot of setup, depending on how you want to run the game.
