You need to be atleast jr.member rank to be able to joing these signatures campaigns and ranking here today is a lot harder than ever before,because it will require you 30 activities which is approximately 1.5months old account here in bitcointalk so you would be able to join these campaigns.But you can still earn stakes from these campaigns by joining social media campaigns like twitter,facebook,and telegram it is much easier to participate than signature campaiogns which will require you to posts here in bitcointalk.