When you install an SSL cert on a domain name you typically need to create redirects in the code to funnel visitors to the https version of the website.
With Wordpress however, a plugin is available that can do this task automatically. The plugin is called 'Really Simple SSL' and it can be gotten here:
You'd want to install it after the SSL cert has been installed on the domain name to avoid any issues.
You can learn about plugin management in Wordpress here:
You can learn about installing an SSL cert on a domain in cp.blacknight.com here: