How do you play in a all random all mid on league of legends

You can either join or create an ARAM (all random all mid) game by going to custom games. Either create your game with ARAM in the name or look for a game with ARAM in the name. You will be randomly assigned a champion and everyone meets in the middle lane. There are restrictions on what you can do and use; no guardian's angel, no items that have stack effects (20 stacks gives you a stat boost), no waterfalling which is going back to your nexus to heal, no using bushes and no leaving the middle lane.