When posting chant ideas, I strongly encourage you to take the time to google/youtube search, find a video or audio file, and include a link to the song you are basing the suggestion on. That way, people who have never heard of, or are only vaguely familiar with the song you are talking about can have a listen. It really helps get people's head around your suggestion.
1. Copy [Ctrl + C] the url of the youtube.com (or other site) page that has the video.
2. In the message you are composing, highlight the text that you want to become the link.
3. Then click on the link icon (in the red rectangle in the screenshot below)
4. Click in the URL box (in the red rectangle in the screenshot below) and
5. paste [Ctrl + V] the URL you copied in step 1. and then
6. click the [INSERT] button.
Viola. The text you selected will now be a link.