Your PHP needs to have the relatively new DateTime class installed. If you don't know whether or not it does, try the plugin out anyway. It'll check for you and won't install anything if it can't find it.
Upload the bucketlister folder to the /wp-content/plugins/ directory
Activate the plugin through the Plugins menu in WordPress
Go to the Settings panel, and somewhere in there should be an item called Bucketlister
Make some death lists!
Requires: 2.8 or higher Compatible up to: 3.0.5 Last Updated: 2012-5-25 Downloads: 650