 installer un theme et definir des themes par defaut goal install a core theme or a contributed theme that has already been downloaded choose the default themes to use for the site and for administrative pages steps in the manage administrative menu navigate to appearance  locate the themes that you want to use as the site default theme and for administrative pages for each of these themes if the theme is in the uninstalled themes section click the install link to install the theme wait for the theme to be installed translations might be downloaded you should be returned to the appearance page locate the theme that you want to be your default theme which should now be in the installed themes section if it is not already labeled as the default theme  click the set as default link at the bottom of the page select the administration theme that you want to use on administrative pages click save configuration if you selected a new theme if you changed the default theme for your site visit the site home page or another page on the nonadministration part of your site and verify that the site is using the new theme if you changed the administration theme verify that the new theme is used on administrative pages  