Make sure your video's background isn't distracting. Take a look at what can be seen in the frame and remove anything that would distract the viewer from the actual content of the video.
Also, take note of how your coworker looks! Make sure there isn't anything in their teeth and their hair isn't messed up! They'll want to look their best so let them know if there's something that might look a bit off, they'll thank you later.
If your co-worker is feeling nervous or anxious, try and encourage them. Let them know that you can try as many times as they'd like!