Apple posted a new Knowledge Base article late on Tuesday that shows step-by-step how to install RAM in the new 21.5-inch and 27-inch iMac.
Unlike replacing the hard drive or SuperDrive, installing and upgrading RAM in the new model iMacs is a fairly simple process that involves removing a single screw from the bottom of the computer's aluminum body.
The new iMacs include four SO-DIMM DDR3 SDRAM slots and are capable of holding up to 16GB of memory. Full instructions, complete with diagrams, are available at the Apple Support Web site.