If you're having trouble figuring out how to upload to google docs/drive (it's the same thing but they seem to be moving to a different name).  For some reason, they prefer to use an icon without any word like Upload.  It's the icon circled in yellow next to the Create button.  Click on that and a window should open to browse for the file you want to upload.

Once you upload the presentation into Google docs/Drive, open it (it needs to be in Edit mode to see the Publish to Web option--

When various options come up, choose Small size, and then copy the embed code.  

When posting on the blog, use the Html option in the blog window and paste the embed code just before the last </div> sign.