Use the Moodle doc for
Installing a new Theme
This example shows you how to install a given theme that you have downloaded. Later we will look at aspects of developing your own theme.
Remember that themes can be changed in many contexts in Moodle. You may select different themes depending upon the device that will be viewing Moodle. For example, you might have one theme for computers with monitors and another for mobile phones and another for tablets.
Click the button at the bottom of this page to "install" the theme.
The version of Moodle which your site is using can be found if you login as an administrator and go to Settings > Site administration > Notifications.
Your exact Moodle version may be obtained by viewing the file moodle/version.php in a text editor. Here is a typical version.php:Example Moodle version.php file
This theme is currently being used on the Birmingham University web siteEssential