Ha ha ha! Well, this kind soul will tell you how P=
Find a weapon that's between the levels of 101-119. Break it to get the Emerald. That's it.
Now, I'm unsure as to how newb you are (you are likely too lazy to look it up), but upgrading the weapon will INCREASE the CHANCE and the AMOUNT of jewels that you'll get from the weapon. So if you have a +0 weapon and break it, chances of getting that one Emerald is low.
Visit FlyFF Wiki or the official FlyFF website. They'll cover this process in more detail, but I've already informed you of the basics.
Have fun!