I have developed a website for collection of tutorials. Now i am starting with SEO. But i am bit confused whether Should I add both www and non-www version to my google webmaster tool or should I add www version and set the preferred version in it (vice versa).
You should add both. You can add both and the two may show you different information.
It is most important to add the one that you intend having your visitors use. You should pick one "canonical" one. Either redirect one to the other, add meta rel link canonical tags, or set the preferred one in Google Search Console.
The non-www version should be a roll-up of all your subdomains. So if you were to choose just one, I would go with the non-www version.
You should just use one (preferably www.). Google webmasters is smart enough to see what your preferred format is and will make the necessary changes for better analysis. "For instance, if you specify your preferred domain as http://www.example.com and we find a link to your site that is formatted as http://example.com, we follow that link as http://www.example.com instead. In addition, we'll take your preference into account when displaying the URLs."
Read more at: https://support.google.com/webmasters/answer/44231?hl=en
The most important thing is to always use the same version (with www or without) when, in example, you are trying to boost your rankings in Google. And as John said it doesn't matter in the GWT.