Wherever you want to put the outlet drill a small hole.
How to drill down from attic to basement.
When working from an attic space it will be significantly easier to access a wall space on the floor below by working either an interior wall or the exterior wall that is on the gable end of the structure.
Apply firm pressure as you drill through the plate and into the basement crawlspace or attic space.
Begin on the interior drilling straight into the wall wherever the device will be installed once through the first lasyer of drywall bend the shaft so the side of the bit cuts the drywall to about a 45 angle.
Drill hole into wall plate.
It will be next to impossible to drill downward under the portion of the roof that slopes to the attic floor without a right angle drill.
A good way of marking where to drill the hole for your wire is to first drill a small pilot hole from the first floor into the basement.
Right under the outlet where you want the hole for your wire drill a small hole under the baseboard moulding at the joint of the wall and the floor.
Use the coat hanger to see if everything is fine at this location and there are no obstructions.
Now simply push the drill bit in either up or down and keep going until it hit something solid.
Now go up to your attic or down to the basement or crawlspace and drill a hole in the top or bottom wall plate in the same wall cavity as the outlet.