Here’s a quick video by HRDNZ, a Moodle Partner in New Zealand.
The video discusses how to locate themes on Moodle.org, download them, and then how to install them using the admin interface in Moodle. The process has never been easier for Moodle using the admin interface which starts at about 1:45 in the video.
Check it out at https://www.youtube.com/watch?v=K3MYE8am7M4. More videos and training are available from HRDNZ at Moodlebites.com
Note: Moodlenews has no affiliation with Moodlebites.com or HRDNZ