Greeting Hamid
As John Cross and Sander Van Dijcke explained you clearly what you lack and basically provided you with articles to refer, I would like to mention few more points which I think you can follow:
As you are having low domain authority i.e. Domain trust
Focus on Content and convert it into keyword rich (Note: Maintain Keyword Constancy and Don’t Stuff Keywords).
As you are having low domain authority i.e. Domain trust check for any errors or broken links in your Webmaster crawl errors database.
Focus on Social Share and Building links with high page authority.
There are ready available tools, which you can find out whether your website is penalized or not
(http://pixelgroove.com/) Check this out.
And use MOZ Open Site Explore and try to disavow spam backlinks.
Check for website Speed and other small issues using free tools available online
(http://gtmetrix.com/ ). Hope this helps
Thank You