You should read this first about activity and merit system so that you know how activity and merit system works.
https://bitcointalk.org/index.php?topic=2818350.msg28856522#msg28856522And hope you are reading the sticky or pinned thread here first in the beginner's section before you guys posting here in the forum.
Check this
https://bitcointalk.org/index.php?topic=1689727.0Anyway, you can get activity by posting on any airdrop and bounty thread or even in off-topic section.
just make sure that your post is not useless otherwise your post will be deleted including the activity.
Take note activity update is every 2 weeks and you can only get 14 activity maximum every 2 weeks.
If your plan is ranking up your account make sure you know how the merit system works the link above might help you how rankings system works.