My roommate and I just moved into a new apartment and had Verizon FIOS set up.
We assumed that since there were several Ethernet outputs across the apartment that we would be able to just hook up our computers and other accessories to these outputs but we can't. I'm completely new to this kind of thing, and I don't know where to start looking to troubleshoot.
The FIOS provider activates your media converter, a small box somewhere in the apartment attached to a fiber optic line from the wall and also attached to AC.
A) If you rent a router from them, they're responsible to connect and test that router. Here's a very rough sketch of the typical fiber-to-Ethernet-and-WiFi setup when you rent a router from them.
B) If you did not pay for their router rental, it's up to you to connect your router to their media converter with your Ethernet cable, and for you to connect whatever devices you wish to your router. If you do not have a router, you will need one, plus (for every PC or device) patch cables to run from the router to every device (or the the apartment patch panel or biscuit jacks 
the little boxes taped or screwed to the wall or molding which have an 8-conductor jack inside. They don't have eight conductors? Then those are for phone lines, and you can't use them for Ethernet.)
If they are 8-conductor (not 6, 4, or 2 conductors, but really, truly, eight), Look on the biscuit jacks to see if they're labeled, which maybe tells you where their wires go. Could be there's a patch panel or several biscuit jacks all in one place, and if there's either, your FIOS box is probably within three feet (the distance of the commonest Ethernet cable found on a telco tech's truck).
They're not all eight pins inside the jack? They're phone connectors, and you cannot use them for Ethernet. Period.
The jacks have 8 pins, but they're not labeled? Then connect your router to each of the patch jacks or biscuits. When you do this, the light for each of the 4-8-howevermany ports on your router will all be dark.
Go to a room, connect a PC with an Ethernet cable to a wall port there, turn it on, and then go back to the router. If there's a new light on the router, you've connected; if not, tell your apartment manager his wiring's bad. Lather, rinse, repeat.
Gee, that sounds like work. How does an installer do it? They've got a Fox-and-Hound set which let them trace wiring. You don't want to spend the $100 or so to get one.
