when it is finished it displays other people's videos over the top. I am guessing I have done something wrong in setting up my youtube account.
No - you haven't really done anything wrong. This is a default setting for YouTube. If you are serious about creating video, you always need to remember that YouTube isn't actually free. Money may not change hands but you certainly pay and one of the ways is that the system is designed to help you to direct traffic back to YouTube - not to their site.
You may find it useful as this appears to be your first time, to review this article and see if there are any little tips to follow that you don't know; http://sbitips.sitesell.com/setting-up- ... -time.html
Anyway - to answer your question...
When you select the embed code, you will see a little button almost directly underneath that says 'Show More.
In the image below you will see the checkbox giving you the option to show suggested videos. De-select it.
Hope this helps