To have an overlay show and stick at the end of the video you simply need to make sure the overlay shows at the end of the video and then you set it to pause when it appears.
Here is how to do that...
In this particular video, I have a full screen text link overlay appearing at the end of my video.
1 - Since the video I'm using is 33 seconds long, I set the overlay to start at :32 and set the duration to 1 second:
2 - Set the link and the content that you want to show
3 - Enable "Pause video"
You can check out how that works in a real example here.