Not sure if anyone already asked this but I NEED TO KNOW where Rotom is?

After getting the National Dex, go to the Old Chateau on the edge of Eterna Forest. Go upstairs and find a room with only a TV in it. At night, go up to the TV and you battle Rotom. Be careful though, it is only Lv 15

Rotom can be found in the Old Chateau at night-time, after you've beaten the Elite Four and gotten the National Pokedex.

To find Rotom you must wait until nightime. At night, go to the Old Chateu. Bring a Pokemon with the HM cut. Inside, go upstairs and into the center door. In there, you will see a series of doors. Go the the first one on the left. Save and press the (a) button while facing the TV. You will be given the option of thumping the TV. Say yes, you will hear Rotom's cry, and begin to battle him. He is only level 15, so automatically throw a quick ball. If he breaks out, try a dusk ball, or an ultra ball. Now you have Rotom!

Ok here's what you do;

Go to the Old Chateau at night, and go to a room upstairs that has a TV in it. Click on the TV, and hit yes, when it says it looks like a Poke'mon is in there. Rotom should come out. He's at level 15, and should be easy to catch.