[Plugin: W3 Total Cache] what is “manual export to CDN”

If you’re using Mirror as indicated in your other forum topic, then this step is unnecessary. First you need to clarify what type of CDN provider you are using.

You might wanna refer the steps on how to setup your CDN with W3 Total Cache as below link

https://instantcdn.asia/enable-instantcdn-on-wordpress-using-w3-total-cache-plugin/

Thanks @instantit.