As soon as we create a scene7 configuration and click save then all the "_CSS" & "_DMSAMPLE" folders are created under synced folder (default: /content/dam) and same will be pushed into Scene7 server as well.
In below mentioned page I have found the Sample asset manager page link.
https://helpx.adobe.com/au/experience-manager/6-4/assets/using/troubleshoot-dms7.html
AssetManagerPage Link on local AEM is http://localhost:4502/libs/dam/gui/content/s7dam/samplemanager/samplemanager.html
From here we can find the list of assets synced , List all synced assets and List all unpublished assets.
On that page it's mentioned as below.
"The sample assets + preset CSS/artwork are now synced and activated AUTOMATICALLY when DMS7 cloud config is created."