Removing the www from your site URL is easier than you might think. Usually your host will have it set up so that both the www and non-www URLs will work to get people to your site. If your site was set up with a www in the URL and you want to remove it, just go to Dashboard >> General Settings:
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Here you can change the WordPress Address (URL) and the Site Address (URL). Simply remove the www from both and save your settings.
For more information, check out the WordPress codex article on changing the site URL.