Five stars because obviously this is my problem, not the extension's, but...

Out of the box it works, but I can't figure out how to do any of the customization that would make it truly valuable. Like,

① How do I add a search engine? I can follow the instructions, but adding a link to, say, dictionary.com takes me to that address, dictionary.com, not to a search for the highlighted word.

② What do P and C stand for in the "Search Engines" chart?

③ Where can I ask questions like these? A review seems the wrong place, but "Homepage" and "Support site" both lead to the same github page, which isn't for a non-techy like me.