Youtube doesn't allow you to watch a user's videos from oldest to newest in a playlist (unless you create your own by adding each video individually), but by sorting uploads by Upload date (oldest first), clicking on the first video (the oldest one), and adding:
to the end of the address!! I go through the simple process in the following video:
NOTE: This is my first ever video uploaded to youtube, so if it's the digital equivalent of a cave painting, I apologize. Just trying to figure it out! Hopefully if I continue to do videos, I'll get better!