WHY!?
When you install Avast! it sets itself to start automatically when you turn on your computer, you don’t need to set it to launch at login, you get the avast logo on your menu bar at the top right.
For someone who complains about software not working out of the box you are really making it hard on yourself. You are suppose to install avast! and forget it, no need to tinker with it once is set up and running.