The next step we have to take is update the legacy content on your WordPress site. WordPress stores links to pages and images as absoute URLs, meaning that the full URL, including the protocol, is saved in the database. To ensure that the entire website is consistently served via HTTPS (without spitting up warnings about mixed content), you will need to update them.
If your host provides phpMyAdmin or some other interface to run MySQL queries, you could do this pretty easily with a few queries in the SQL tab.
yourdomain.com in the following queries with your actual domain and if you've customized WordPress' table prefix, replace
wp_ with the relevant prefix. Run the following set of queries:
UPDATE wp_postmeta SET meta_value = REPLACE(meta_value,'http://yourdomain.com', 'https://yourdomain.com')
UPDATE wp_posts SET post_content = REPLACE(post_content, 'http://yourdomain.com', 'https://yourdomain.com')