How can I update my theme?

When visiting the Dashboard Updates Screen, if there are updates available for one or more themes (active and inactive), this message displays:

The following themes have new versions available. Check the ones you want to update and then click “Update Themes”.

Please Note: Any customizations you have made to the Themes files will be lost. Please consider using child themes for modifications.
After checking Themes (to Select All), or one or more themes, click this button to begin the automatic upgrade process. The following messages will display during and upon completion of the upgrade. Messages for each theme being updated will display