Log into your Drupal site.
In the Admin bar at the top, select Manage -> Extend
Step 3 (optional)
If your drupal instance do not have Update Manager by default, install it via Extend modules.
After you've downloaded the CDN Module from Drupal.org, select "Install new module" and upload the .zip.
Go back to Extend page, scroll down to Web Services section, checked CDN and CDN UI , clicked Install
Hopefully, everything will install successfully. That's something your hosting provider can help with.
Once the CDN Module has been successfully installed, from the top admin bar, go to Manage -> Configuration, scroll down to Web Services section, select the CDN Integration
In the CDN Settings Page, Enable Serve files from CDN, and save
In the Forever cacheable files, disable Make files cacheable forever ( if we enable this, this will lead to files failed to served on the initial setup
In the Mapping, select Simple Mapping, serve all files , enter the CNAME record generated when you created a CDN resource into the from field, and save the Configuration. See How To Set Up A CDN Resource.
Your done. Test the configuration and run a Pingdom speed test.