How to start Cloud optimization?

It will still use some server resources, because it has to query and update the database for each image optimized, but this is minimal compared to the image processing that is occurring offsite. If you have all the cloud boxes check, and a valid key entered, it is using the cloud optimization. The advanced compression is optional though. The Bulk Optimize is the right place to start. You should watch the videos on the Installation page (they were also linked in the welcome email).