then go in the attic and find a junction box that you can tie into and then join up, make sure you wire nut the wires back and tighten up the cover,then run your line to the center of the ceiling, have a coat hanger sticking up from the inner room for center location, poke the line down the hole, then shore up the area for a ceiling fan mounting and electrical box and your set. This will only work for pull chain operation of fan and light kit. There is no switch on the wall for this.
Like I said, this is for a quick fix.
Now, if you want the fan operative via a wall mounted switch and since there in NOT a light on the ceiling you have a much more complicated operation and should probably consult an electrician, you have wall boring issues, running cable up the wall and all.