On the right side cover in front of the foot peg. There is a little round cap about 2 inches in diameter at the front of the casing cover. It has 3 allen screws in it. The oil filter is under that cover. Make sure the new filter goes in the same way the old one came out or as it is outlined in your Clymer's Manual. If it isn't put in correctly, it will not oil the cam shafts and lifters and the engine will seize. That is one reason you always losen one of the oil lines at the head to make sure you are getting oil to the upper end following an oil and filter change.
Bill