PLEASE NOTE: Feng Office comes only with the default theme.1) Therefore you won't be able to select a different theme unless you download one elsewhere or create your own theme.
Selecting a theme is done in the administration panel (Configuration > General). You have to reload the page afterward to apply the new theme.
To create a new theme simply copy the folder with the default theme (
public/assets/themes/default/) and name the copy according to the name of your theme (i.e.
public/assets/themes/mytheme/). Obviously you have to modify the files in that folder first to see any difference.