The bit of information that I was missing (and I’m posting it here in case it helps someone who comes by here in the future): after dropping the plugin into your Plugins folder and opening the project again you don’t see the new plugin in your Content Browser.
You should now go to Edit->Plugins, And under the Project section you will see your newly added plugin.
And now you should check the Enabled checkbox.
It will now show up in your content browser.