The best way to do a digital presentation is by using Screencastomatic (here is how). It does not require an account and can immediately be uploaded into Youtube. The only problem is that some schools do not allow use of Youtube. If that is the case you have a free alternatives:
About two months ago I posted a video George Coe did on how to save a video within Google Apps. But the video did not show you how to create an audio presentation. So if you go to the video above I used Photo Story which is on any computer that uses Microsoft. Once I show you how to create the presentation I also show you how to upload it into Google Apps or Google Docs, if you do not have access to Youtube.