Update the Main Domain / Primary URL of a WordPress Website
When you update your WordPress site to use SSL, or change the primary domain name of your WordPress hosting account, you will often want to update your base WordPress URL. To do that, just follow this guide:
Step 1 - Log in to your WordPress admin section
Step 2 - Click on Settings > General
Step 3 - Update the WordPress Address (URL) and the Site Address (URL) field
Then scroll down the bottom and hit Save Changes
Step 4 - The last step is to update all the URL's using the Velvet Blues plugin. Install and Activate the plugin.
Next (1) Click Tools then (2) Click Update URLs (3) Add in the Old URL and New URL (4) Tick all the boxes except the last (5) Click Update URLs NOW