The first thing you need to be able to participate in the signature campaign is a  account own the rank from Jr.Member and up in this forum. Then you can refer to the campaigns in Marketplace (altcoins), just read and follow the steps to submit the registration form as well as set the signature for your posts. After that you become a member of the campaign and you can post your posts to the forums to receive rewards from the campaign. However, I think you should refer to some video tutorials or ask someone you know to help as it will be easier for us to sit and write on these lines.