I got it just before Christmas '13 upgraded specs 8gb ram one
Then you do not need the
optical disk drive (ODD) yet, if you want to boot into Mac OS X or Recovery Mode.
Okay, since the links do not seem to work, we can do it this way:
Shut down your Mac by holding down the power button.
Start the computer by pressing the power button.
Immediately press the OPTION/Alt key.
Select which OS to boot from via the arrow keys.
Press Enter.
If you chose Mac OS X to boot into, it should be fine then.
If not, shut down the Mac again and press the power button to start it again.
Immediately press CMD+R to boot into recovery mode and select Disk Utility from the Utilities menu.
For further information about recovery mode and such, you can look at the links I provided, or the quote in post #4.