To be a merit source, you need to apply for it. If your application is accepted by the admin, you will be a merit sources for the location of the forum where want to specialize. Lol, you merit yourself to the rank of a hero, you can't merit yourself except you trade the merit with other members (i.e you send them $merit and they in return send you $merit) and besides if you become a merit source and you abuse the merit system, you will be stripped of your post as a merit source.
To the OP, I wish you well in your application but you should know that being a merit source is not an easy task. It requires lots of time to go through all the posts in the section of forum where you applied to be a merit source.