To perform these steps you will need a putty knife and a #00 Philips Screwdriver.
Unplug the Mac mini and place it upside down on a static free work surface.
Insert the putty knife between the upper and lower case and work your way around while prying outward. You will hear a series of pops as the clips that hold the cover in place detach.
Once all the clips have been loosened you can flip over the Mac mini and pull the top cover off.
Inside the cover you will see three antennas labeled with orange stickers. There is one at the bottom left, top left, and top right of the device.
Remove the top left antenna by gently pulling up and setting it to the side. Remove the spring under it and place it to the side as well.
Do the same for the bottom left antenna.
To remove the top right antenna you must squeeze clip under it then pull up on the antennae to release it. Don't forget to remove its spring as well.
Gently disconnect the ribbon cable from the back of the disc assembly. The connection is located at the top left of the assembly.
Next we will remove the four screws holding the disc drive assembly in place. There is one screw at each corner of the device. Please note the bottom right screw is slightly longer then the rest.
Set the screws to the side then lift up on the disc assembly to remove it and reveal the RAM.
Gently push on the two arms holding the RAM in place to release the memory stick.
To insert the new RAM make sure the notch at the bottom of the memory stick matches the position of the notch in the memory slot. Push the memory stick into the slot until the arms click into place.
There are two memory slots which can be used in the Mac mini. The device takes 204-Pin DDR3 SO-DIMM 1066 (PC3 8500) type RAM.
Once you have installed the new memory you can set the disc assembly back in place.
Replace the screws you removed from each corner earlier. Remember the slightly longer one goes at the bottom right.
Reattach the ribbon cable to the back of the disc assembly at the top left of the assembly.
Place the three springs on top of the antenna posts at the bottom left, top left, and top right of the device.
Next put the antennas back in place on top of the posts. Remember to squeeze the clip on the top right post when putting the antenna in place.
Put the top cover onto the bottom of the Mac mini and press down to reattach the clips.