Majority of bounties won't allow a newbie in rank to join their signature campaign because of the small signature space and not so visible link to the forum members.

It's not also clickable.

Check those bounties if there are some of them who are accepting newbies in rank. But in your rank, you don't have focus with signature campaign's, you can join the other types of bounty like social media.

This list is not updated at all so better to check the section or bounty websites alone.