Add a Video

Preceden currently does not support embedding videos on your timelines. Your best bet is to paste the video's URL into the event notes. Preceden will automatically convert that URL into a link, so anyone viewing your timeline can click it to watch the video:

An Add Event dialog with a YouTube URL pasted into the Notes field

To show something other than the raw URL, write the link with Markdown so it displays the words you choose: Add a Link to Your Timeline.