Well to be honest into the attic and down to the room.
Just keep the cables away from mains electrical runs, for the lighting circuit for the upper floor.
And if your fussy use some cable trunking to smarten it up a bit for the run from attic down the wall of the room intended.
Either option will work, but as stated running it through the attic would be the better looking option.
The main thing to look out for here are possible interference such as running it over electrical cabling, close to air cons or anything that can give out electrical interference. If you won't be able to stay clear of interference, you might have a look at a STP (Shielded Twisted Pair) cable that won't get interference, but they cost more.