Its a lot easier than playing on game consoles, for me anyway.
You just pop the disc in, it installs the game (usually you don't need the disc after that, you just click on the game icon). Once it installs you open the game and have more settings like screen resolution and you can set which buttons preform which actions. If its like CoD, the mouse corresponds to where you're facing, as well as where you point your gun. There's no auto aim

Usually the "w" key is to move forward, "s" to move backwards, "a" left and "d" right. Use combinations of these to move in diagonals. Then usually numbers are to switch weapons. Like 5 is to switch to your grenade launcher and 6 is for special grenades. G is for grenade. Its really nice because you have all the buttons in front of you, you just need to learn which buttons do what.
Theres my little essay.