In this video, we see that how to install a Moodle Theme and do customisations.

Site administrator inside a Moodle site who has access to the Moodle code can easily install a new theme Moodle theme.
You can 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. To change themes, you can visit at below links :

1) Open Settings Site administration Appearance Themes Theme Selector
2) "Select theme" button on the right of the current theme
3) Scroll down to find the theme you wish to use
4) Click the "Use theme" button next to that theme
5) Check your Moodle site by going to the Moodle site's home page.
6) Refresh or hard reload the browser if you do not see any changes.

Custom themes are available for download from the Moodle Plugins directory on the link below:
https://moodle.org/plugins/browse.php...

Boost Presets Settings :
https://docs.moodle.org/dev/Boost_Pre...

Fordson Theme Settings:
https://docs.google.com/document/d/1Q...

Read more about moodle by visiting :
https://docs.moodle.org/311/en/Main_page