To find the template you have created navigate to the 'templates' menu tab and scroll down the page until you see 'saved templates'. This is where all your saved templates will be stored. Once you have found the template you would like to use, click 'create video'. This will bring up a form allowing you to type in your new content and choose your new background media.
Please be aware that as default the original content and background media will be chosen.
Once you have finished entering your video information click 'finish' and your video will be returned back to you shortly.