If you want to enable SSL (Secure Sockets Layer) in your WordPress website, first you need to install SSL Certificate.
Step 1: Login to your website.
Step 2: While you're on your WP dashboard, click on Settings and go to General
Step 3: On the General page,you'll see two fields - WordPress Address (URL) and Site Address (URL). In the WordPress Address (URL) box, change http:// with https://, and in the Site Address (URL) box, supersede http:// with https://.
Step 4: Finally save the changes by the use of Save Changes button located on the bottom part of the page.
Now, you have successfully enabled SSL in your WordPress website.