I searched the Blogger help groups and found this information.
You would need to upload the powerpoint somewhere and then place a link in your post that says Download powerpoint presentation here.
The key seems to be that your PPt has to already be located somewhere on the web. Using Ellg as a host and snipURL to shorten the URL, I was able to insert a PPt in the sidebar. Now I'll try to insert it here in this post. Quest Garden Tips
Okay. By using the same html code that I used in the sidbar, I was able to insert this PPt in the post. It's very unnerving because I am just copying code without knowing what it means. To do the same thing in Word Press is much less comlicated.