Since many people have had problems uploading, here is a step-by-step guide which should work:
1. Register yourself at:
http://www.slideshare.net/signup1b. Login
2. Upload your slide at:
http://www.slideshare.net/singleupload (the default "bulk upload" did not work for me)
2b. Wait for slideshare to process slideshow
3. Go to the Media Ecologies Event at:
http://www.slideshare.net/event/media-ecologies4. Below the current slideshows there is a textbox which reads "Share something, intr..." and below it is some text saying: " Add a slideshow (optional): Paste URL or use slideshow finder". There click the "Paste URL" link, and it provides a little textinput.
5. Enter the slideshare URL to the presentation you uploaded into the box. For example the URL which slideshare provided for my slideshow was "http://www.slideshare.net/steinnes/threshold-of-confluence", enter something like "Here is my presentation" in the bigger textarea above, and click the "post" button to the bottom right of the form.
To find the URL to your slideshow after it uploads, you can go (while logged in) to:
http://www.slideshare.net/my-slidespace and copy the URL (right click, choose "copy link location" if using firefox).