I suggest you take some time to play at least one game with the easy (mechanically) champions like annie, garen, amumu, master yi, brand or ashe. If you are a complete beginner, then picking a specific lane does not really matter. Then you can stick to the champ that got you the most excited and spam the s**t out of it until you understand the mechanics behind it. My advice for you is to focus on killing the minions, learn how to execute them and how to safely cast your abilities.
GL HF