I can't answer your question without a wiring diagram, but you can get taps
for blade-type fuses and insulated crimp connectors for the taps at auto
parts stores.  Tap the fused side (the side that gets disconnected when the
fuse is pulled or blown) of a fuse that is always hot, like the dome light;
connect a female insulated blade-type crimp connector to a wire and connect
the wire to the accessory socket.  Look at the back of the socket for a
connector that will fit, and unplug the factory connector.  This way, you do
not disturb the factory wire harness and can easily return it to factory
condition when you sell the car.

 If you are plugging in small things like a cell-phone charger, go
get an Accessory Power Socket to mount under the dashboard, a small
spool of #14 wire, an inline ATO fuse holder with a little plastic
flip cover for the fuse, a 10A ATO Fuse, and an "Add-A-Tap" adapter.
A few barrel crimp connectors and a pair of electrical stripper
crimper pliers.

 Oh, and get an ATO "Spare Fuse Kit", so you have an assortment of
extras with you at 2AM, throw it in the glove box.  Use an ATO inline
fuse holder, for the simple reason that you only need one kind of
spare fuses to match what the car uses.  No box of spare 3AG glass
fuses to add to the clutter.

 Mount the socket somewhere knees and legs won't be hitting it.  If
the dashboard isn't grounded steel in that location, hook a wire to
the baseplate and go to the main body ground bolt, usually in one of
the cowl panels in front of the doors - where your outboard ankle is
when seated.

 Run the lead from the +12V center tab of the accessory socket over
to the fuse box, tying it up out of the way of sharp edges and moving
parts (like the brake pedal linkage) with nylon wire ties.

 Splice the power lead to the in-line fuse holder, and splice the
other end of the fuse holder to the Add-A-Tap.  With a test lamp
(looks like an icepick with a ground wire on the handle) find a fuse
that's constant on, like the dome light.  Remove the fuse and figure
out which end is the power in, and put the end of the Add-A-Tap with
the tap wire on that end.  Replace the Dome fuse in the fuse socket
part of the Add-A-Tap.

 --<< Bruce >>--

 (And remember NEVER GO BIGGER than the fuse holder markings, if you
plug in the fuse and it pops immediately there is a problem that must
be fixed.  Try to stick a 30A fuse in a 10A slot "to get home" and you
could start a nice electrical fire and totally destroy the vehicle.
$3,000 worth of damage usually totals out most cars.)