This is guide to help you if you are wanting to go self-published, these are the sights I have been using for the past 8 to 10 years, they are all 100% free to publish with and completely safe and reliable.
Paperbacks Lulu http://www.lulu.com, they do lovely perfect bound books. I have been with them for 10 years. My biggest TIP books, this is including covers, need to be formatted in A5 saved as a A5 PDF for the book to be rendered properly when converted into a paperback. It does not format A4 PDF's very well at all. I always write my novels and create my covers in A5 to save having any problems when publishing with them. Covers need to be saved as JPGs.
Lulu also does ebooks, however it can be a frustrating and time consuming task to get your story accepted by all the sites they offer, I always struggle to get my books to be accepted by nook and kobo no matter how much reformatting I do my books never get accepted by those sights, this is why I just recommend lulu for paperbacks less hassle.
Ebooks Google Play I'll give you the link to their publishing page as it can be a little hard to find on their sight https://play.google.com/books/publish/
They are just awesome I have been with them for around 9 years, they will publish your book with 79 countries, and it is so easy, no formatting to do, you just put up a JPG of your cover and a PDF of your manuscript and in 24 hours you are published.
iBooks, I have been with them nearly 9 years, you will need to download iBooks Author and use their templates you can change it to how you want the book to look, tip redo your cover from scratch this will save it looking out of forces or have a border when using a PDF or JPG.
ePubs Kindle https://kdp.amazon.com/en_US/ I have been with them 8 years, Warning getting your document to format with them right can take some time, it needs to be a plain simple document, no text boxes and covers need to be saved as a PDF. The manuscript needs to be exported as an ePub. They are another site which I am afraid it is better if you use A5 as again it does not care for A4.
Huge tip, make sure you have plenty of time when using Kindle, I always make sure I have a few days as that is how long it can take to format your book so it is looking how you want it when viewing it on there sight, it is nice you can save it as a draft and come back to it later or when you are just needing to take a break as trust me you will be scramming at your laptop in no time.