In another tab/window, go to the citation generator, click on the 'An arbitrary website' bubble, and fill out as many fields as you can about the bare URL.
Click the 'Get reference wiki text' button.
Highlight, and then copy (Ctrl+C or Apple+C), the resulting text (it will be something like <ref> {{cite web | .... }}</ref>, copy the whole thing).
In the Wikipedia article, paste (Ctrl+V or Apple+V) the text you copied, replacing the bare URL reference.
