Download Quick Media Converter.  Inspiration allows you to add videos to projects but they need to be one of the following formats: .mov, .avi, .mpeg. These are very common formats, but you will need to convert videos that are in one of these formats (ex. .flv youtube videos) to one of the compatable formats in order to use them in an Inspiration project.   This software is the best and easiest way to do just that.  

http://online.movavi.com (online file converter)