You should post messages regularly. By doing that, you will increase your activity. You will be Jr. Member when you reach 30 activity. After that, when you reach 60 activity you will be Member. After being Member, you will need merits from other people to increase your rank. Activity will not be enough to increase rank.
i just need to make 30 activity only by posts? and i will growing up?
Do not misguide someone with a non working easy looking formula. To level up you need to prove yourself to the community and get merits. Just post as per wish and expecting something from the community is not a good approach.
Merits play a major role. There are lot many users in who have 100+ activities and are not yet Jr Members it is because of lack of merits. Please cross verify info before sharing.