I have used a snip listed below from the tutorial - Theme - Change or Save that lists the locations of where your themes are stored . Navigate to the locations of your saved themes and copy & paste your saved themes to each of the other users folder located at C:\Users\User-Name\AppData\Local\Microsoft\Windows\Themes
folder. Each user may then have to navigate to their user folder containing the new themes (location in bold print above) clicking on each theme once to enable it in Personalization if not already shown in Personalization.
Make sure you have show Hidden folders enabled and also if you have Themes that require theme patchers or third party tools to function they may not work properly since the other users are using a non administrator account