You have to install another plugin for this one to work – minimax, a minimal ajax library. MudSlideShow is an image gallery system using Picasa and/or Flickr.
Once installed, its adds a button beside the formatting toolbar. You need to input your Picasa/Flickr username and it will fetch all available gallery from there.
Here’s a sample gallery below.[mudslide:picasa,0,102474,5465706373690627441,576,left]
Thanks to Sebaxtian for this free plugin!