If you want to be a Jr. member then you have to answer other members question with quality answers, If the other members like your posts and answers you can grow your position from newbie to Jr. member.
You don't need Merit point to rank up to
Jr. Member you just need to earn
30 Activity point, that you can acquired by posting more than 30 quality post and also you need to be active in 3 period of 14 days =
42 days