Epson EL 3S/33 - Manual (Page 17)

If you purchased any optional equipment that goes inside the
computer-such as option cards, memory modules, a hard
disk, or a diskette drive-you should install these devices
before you connect your computer. See Chapters 3 and 4 for
instructions.
Connecting the Computer
Use the illustration below to locate the ports on the back of
your system as you connect the keyboard, monitor, printer, and
other devices.
monitor cable
AC outlet
COM1 COM2 PARALLEL GAME
Setting Up Your System 1-3