Hi
Please have a look at this documentaiton :-
Link:- https://docs.adobe.com/docs/en/aem/6-1/author/author-environment/user-properties.html
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AEM provides you with the capability to configure your account and certain aspects of the author environment.
And the community article covering it is :-
Link:- http://aempodcast.com/2014/aem-interface/switching-user-interfaces-within-aem-6/#.VmqPTHYrLRY
To have all users of an AEM instance use the Classic UI by default, start off by going to the AEM Web Console Configuration (/system/console/configMgr). Make sure you’re signed in as an admin and do a find for “WCM Authoring UI Mode Service.” If the service is not visible, click on the OSGi button at the top followed by Configuration, and then do another find. Click on “WCM Authoring UI Mode Service” and change the “Default authoring UI mode” to “CLASSIC” (or back again to “TOUCH,” depending on what you want to do). You must enter “CLASSIC” or “TOUCH” in uppercase letters or an error message will show up when opening a site. Changing this setting will make the chosen UI the default for all sites of the AEM instance. When opening a site with /siteadmin, or /sites.html/content, the site should now open using the Classic UI. This should be the case for all users.
I hope this would help you.
Thanks and Regards
Kautuk Sahni