According to what is shown in the episode Half Loop, the insertion is performed by a surgeon in an operating theater within the Lumon building. The patient is awake but under local anesthesia during the procedure. After making an opening in the subject's scalp, the surgeon uses a drill to make a hole in the back of the skull. A package containing a sterilized chip is opened. The surgeon inserts the chip into a specialized needle using surgical tweezers. The needle is guided by the surgeon deep into the patient's brain, in the vicinity of the amygdala. The chip is placed and apparently locks into position via anchors that automatically deploy.
The effect of the procedure is that one's “perceptual chronologies are surgically split.” Memories from one's work life and one's personal life separated. Access to either of those kinds of memory is spatially dictated.
The alteration is allegedly comprehensive and irreversible.