Hello mate, welcome to the forum, better to try to read first the rules and regulations of the forum, there are already some links commented above just make sure that you have read some of it, merit can be gained once you are creating a good post, just be yourself and share your knowledge that makes you earn merit.
Merit is very easy to get once you follow the rules of this forum and make sure you post and comment a reasonable post and make sure your post make sense for other people to gain from it.
Merit is easy? then why don't you have even one?