You can publish your book with the help of below methods

1- Publishing Your Book with the Help of a Literary Agent

There are many agents available in the market you can do market study and find out your agent. If the things are good in both ways you can sign a contract with your agent. After, that you can start marketing your book. 

2- Publishing Your Book by Contacting the Publisher Directly

You can write the query letter to the publishers. You have to introduce your book and you have to write a brief synopsis. If they like your work you can sign a contract with the publishing house. After, all the thing you can start marketing your book.

3- Self publish your book

You can look for self publishing companies. You have to create a account with the company that works for you. Write your book on Microsoft Word or other programs like that. Choose the size and type of book you would like (paperback vs. hardcover). After, completing all these things you can make your book available for purchase.

All the Best!!