I'm renovating a vintage 1950 house, and just bought a router (a trim
router, to be specific). I don't have any bits for it yet. Now here
is my stupid question:

How do I use it? Pictures or a video clip would be nice.

I mean I know what you can do with a router, but it's not obvious from
looking at it exactly how it works. And should I have gotten a plunge
router instead?
The onlt thing I can think of at the moment that I really want to do
with it is rouer out a little bit of wood on my cabinet hinges because
my new cabinet hinges leave an air gap slightly larger than the old
ones did.