It may also depend on the Privacy setting for the video that you created. If it's Private, I'm not sure if a link is available. In your My Videos list (in the YouTube app), tap the 3 dot button associated with the video, then Edit, then look at the Privacy setting. If it's Private, change it to Unlisted, then Save. Now tap the 3 dot button again, and then Share. You should have an option to copy the link there.