This was very confusing for me. In order to save you all some trouble this is how you do it.
You need to already have python installed so that it can be called from the command prompt.
Download your 3rd party plugin as a zip. ex. AutoRemovePlus
Extract that plugin to a folder.
Shift right click in the folder and click "Open command window here"
Now run "python setup.py bdist_egg" - this will created a folder within that folder called dist.
Open dist, in there you will now have a file called "AutoRemovePlus-0.5-py2.7.egg" it might be 2.6 , make sure you rename it to whatever version of python your deluge uses. prepaidgiftbalance Version Check
Now follow the instructions to install that egg file as you would any other deluge plugin. Deluge Plugin Install
You should now be able to use the plugin.