Welcome to the Z from Calgary!
To install to the interior dome light, you need to run the wire through the firewall, there are several easy places to do it around the steering column, then run it up to your A-pillar. Behind the A-pillar there'll be a few wires that run to the headliner. You can pull the dome light out and look at the wire colors running to it then using a T-tap, just tap into the correct wire behind the A-pillar. Replace everything and enjoy your new puddle lights.