Take the mounting bracket for the smoke detector out of the packaging. Typically, it is on the smoke detector itself. One half of a unscrewing rotation should disengage it.
Hold the smoke detector bracket against the ceiling where you want to install it. Experts recommend placing it near the stairwell leading up to the attic from the floor below.
Screw the mounting bracket to the ceiling using the screwdriver and the screws enclosed with the smoke detector. You may use drywall anchors if necessary.
Replace the batteries in the smoke detector, if desired. Dependent on how long the device has been sitting on a shelf, the included batteries may be less than fresh.
Install the smoke detector onto the mounting bracket by attaching it using the reverse motion that you used to remove it.
Replace all the smoke detectors in the house with more of the wireless interconnectable kind to ensure that if one is triggered, they all sound. This is especially important in a remote area such as an attic, where someone may not hear the lone attic alarm going off.