SSL certificates are necessary for HTTPS connections. This article on SSL might be helpful.
You can ensure your WordPress installation is secure once you have an SSL certificate installed by following this quick guide.
- Log in to your WordPress installation.
- Click "Settings" on the left hand side of the page.
- Find the two fields marked "WordPress Address (URL)" and "Site (URL)" and ensure that your URLs begin with "https" rather than "http".
- Click the blue "Save Changes" button at the bottom of the page.