There are a substantial number of detailed help pages available in Academic Video Online. These can be accessed by clicking the in the top right corner of the page. This opens a menu where you can select:help for the current page or go to ProQuest's support centre. Other options are available, but other than the Training (LibGuides) link, you're not likely to use them.
The help pages are not specific to Academic Video Online as all other ProQuest databases work in the same way, so don't expect to find anything specific to Academic Video Online. That said, the pages are extremely detailed.
The help pages open as a pop-up pager, so make sure you have op-ups enabled in your browser options.
On 16th June 2022 Ali Nazari-Nouri, a ProQuest trainer gave a session on using Academic Video Online. The recording of that session is below