When you have finished your export, you will receive a link to view and download your exported video.
On this video viewing page, you also have several options to share your export to the outside world.
First, make sure you have set the privacy to public to allow external sources to view your export. You can do this by clicking on the lock icon. If the icon already shows an unlocked lock, your export is already public.
You will see sharing options appear if your export is public. Click on the Share button for an embed code.
In this popup you will see a direct link to your export, as well as an embed code that you can use on an external webpage.
NOTE: If you are trying to embed the iframe into WordPress you will require a plugin for the iframe to work. Please see here for more information https://wordpress.org/plugins/iframe/