Examine the eaves of your attic with a flashlight to determine how well insulated they are. Look at the underside of the roof sheathing between the rafters. If there are no soffit vents present, you will need to install them before adding insulation. A soffit vent is a plastic sheet stapled to the underside of the roof sheathing. It prevents insulation from blocking necessary attic ventilation.
Install soffit vents, if needed, by stapling one to the underside of the roof sheathing in each bay between rafters. Be sure that the bottom edge of the vent extends farther than the insulation will be.
Add blown-in cellulose insulation in the area around the eaves by aiming the hose nozzle into these areas and filling them with cellulose insulation. Be sure that the top edge of the soffit vents you installed remain above the level of the insulation.
Install batts of fiberglass or mineral wool insulation against the eaves if you are using this type of insulation rather than blown-in cellulose. Batts should be installed perpendicular to the ceiling joists so that they don't fall in between the joists, compressing the cellulose underneath them. Press the batts into the triangular area created by the junction of the rafters and the ceiling joists, making sure that the upper edge of the soffit vent remains above the tops of the batts.