No matter what kind of publisher puts your book before the public, promotion done by you is a must. There are many avenues you can explore. Some are free and some are costly.
There are advertisements in magazines like RT that readers like to browse and see what new books are available. There is often a review of your story to accompany the book.
There are places like BookBub where you can promote a book that generally you have put on sale. This kind of promo can be costly but many people feel the promo bit is well worth the money spent.
There are blog tours, often run by a company who sends you to other blogs where you can promote your book and also garner reviews.
There are reviewers, both pain and unpaid who can help give your book the spotlight for a time.
You can offer a prize, often a gift card or a copy of your book.
You can find people who will give you space on their blog. These are often free.
There are lists to join where you are permitted to talk about your books.
You can create a news letter to spotlight your book.
Sounds like there's a lot to do. That is very true but unless you get the word out about your book, few people will read what you've written.
For me I take a day and do what promotion I find. I also have a blog and feature one of my books every week and send word to the many lists I have on Facebook, Twitter and other social sites. Though you may hate to put yourself out there, you must grin and begin to find people who want to read your books.