you should have much reading about bounty campaign, especially signature campaign.
first I have to ask u is what makes you confused about. to post signature code or campaign?
to join signature, you have to use the signature code of the project you join. it can be put on forum profile information.
then you can post based on the rules given by the campaign. for instance in altcoins. most campaigns prohibit the participants not to post in politics and society, even in off topics. therefore you have to avoid it to get stakes every week.