Getting your book in the Bounty Library is super simple.
After you've added your book and it's been approved. All you need to do is click on the button "Start A Bounty."
Depending on the options you selected when setting up your book, you'll be able to choose what type of Bounty Contract you want to put on your book.
Check out: What do the different Bounty Contracts mean
As long as you have Bounty Points, you can put out as many Bounties as you have points to spend. Think of Bounty Contract as a request for a review for your book. The more Bounty Contracts you have in the library, the more reviews you can get.