You need to post to increase activity because the more you post the more posts you post will increase your activity. However, there is a certain age limit for increasing the activity of the account, that is, if you just create an account and only if you want to increase the activity as you want by creating the account, it will not happen. If the account is not aged, the activity will be locked to a certain place no matter how many times you post, and the activity will be unlocked when the account is aged again. However, if the account is of sufficient age, activity will be added to your profile as per the posts you post.