While it is simple to add a link to a secondary video in a tag on your primary video, embedding will create a much smoother experience. Viewers can watch the second video just by opening the tag, no need to click through to another page.
To embed a video in your tag:
After uploading your video, click add new tag to create a new tag in your video.
In the link field paste the embed code for the video. This can typically be found within the sharing information for a video hosted online.
Save your tag.
Now the video will be embedded in the tag. After the viewer clicks the tag, the second video will open and all they need to to do is click play.