Simply edit your .htaccess file in the root of your WordPress site and add the following lines on top.
Header add Access-Control-Allow-Origin "*"
Header add Access-Control-Allow-Headers "origin, x-requested-with, content-type"
Header add Access-Control-Allow-Methods "PUT, GET, POST, DELETE, OPTIONS"
Then it should be like this.
Test your site again by clearing your cache.
Hope that's clear.