With any squirrel problem you should first do the things that help your situation.
Keep squirrels out of your attic.
You may also want to invest in a squirrel proof bird feeder that prevents these critters from gaining access to the bird food.
First remove any bird feeders secure the garbage cans and cut the tree limbs back around the house so squirrels do not have easy access to the roof.
Trim trees near your roofline trimming trees near your roofline can help prevent squirrels from getting on your roof and into your attic.
Change food in your bird feeder if your bird food contains sunflower seeds corn or nuts consider changing the type of food as these ingredients attract squirrels.
Prevent squirrels from climbing the tree by fastening a two foot band of sheet metal around the trunk six to eight feet above ground.
Then you need to make the attic unattractive to them.