Issue with www and non www

After doing a analysis on my website I found that www and non www versions are treated differently now.

I have checked non www version has less backlinks and when checking for backlinks it says that error and have no backlinks

When I check with www it shows 840 backlinks

so main question is should I forward non www to www or vice versa

in google search when keyword is searched website is on 3rd page but the url is without www.

Please help





Duplicate Content (www redirect)Error Found
What we found:Wait! We're detecting that you're not redirecting the non-www version of your website to the www version (or vice versa). By not doing so, you're creating essentially two versions of your website that can confuse the search engines when it comes time to rank your site.
Effects on traffic:Smaller infractions of duplicate content, like the www redirect (the one we're looking for here) can have a moderate impact on traffic. You may see after doing the proper 301 redirect from www to non-www (or vice versa) will result in moderately better rankings. Actual duplicate content, where you post the exact content on two different websites for instance, have a much higher impact. It is highly likely only one of those sites will rank with the content, and a small chance that both will not rank at all. Avoid duplicate content!