Look for the bounties that are accepting Newbie (only some accept newbie) then you have to join signature bounty campaign. Every bounty have their own rules and regulations.
Read the rules and apply for signature campaign

It's better to up your rank to at least Jr. Member by being active and exploring the different sections/boards of forum.

Once you will become jr member, you can join most of the bounties. (as  minimum requirement is of jr member for signature campaign) As your rank is increase your earning will also be increasing.