If you can't turn a computer on, you shouldn't being using a computer. There, I said it.
PS, I've worked in IT support for 12 years, I have no formal qualifications. Today, I installed some SSL certificates on a load balancer to get an internal website working on port 443. I did not know how to do this, so I learned. Using Google.
Exactly I'm self taught on everything from CAD to SQL the trick is not to worry about doing something wrong and just see what happens when you try something.
Give this a go as it should help with the basics and there are more advanced ones on the site also
http://bookboon.com/en/business-ebooks/office/microsoft-office-powerpoint