It should be noted that these guides are written based on a late-model eMac (2005, 1.42GHz, DDR). They will differ slightly from the older model eMacs that use PC-133 RAM.
Lay the eMac screen-down on a flat surface. I've found it convenient to use a carpeted floor because the computer is so heavy.
Remove the single phillips #2 screw on the RAM door, and remove the door
The screw is captive in the door, so don't worry about losing it.
Before starting this process it's important to note that the eMac can have some seriously dangerous voltages inside of it, thanks to the CRT display. Before working on an eMac, you should unplug it, press the power button to clear any stored charge on the motherboard, and then let it sit for 24-hours (or more) to allow the CRT to discharge.
You can read more about CRT safety procedures here. If you aren't experienced with working on devices featuring a CRT, it's recommended that you don't proceed any further.
On the bottom side of the eMac, remove the following screws: