As a Verizon FiOS customer, the installation should have included one of their home routers, which has both 4 Ethernet ports & wireless capability. So, connecting any of your home devices should just involve connecting to the wireless ID broadcast from that router (wireless) or plugging their existing CAT5/6 cables into the back of the router (wired). In either case, FiOS tech support can help you with that.
If you mean that you wired up your rooms for Ethernet, then a) hopefully you had the technician install the FiOS connection near where your previous provider let you have your old router so that you can connect the existing hardwired connections into it, or b) you'll need to hire a contractor to come out & string new CAT5/6 cables from the old connection site to the new location of your FiOS router. In this case, don't call FiOS tech support; it's not considered a "technical issue", since they expected you to tell the install tech if the initial site wasn't going to work for the router (especially since they usually end up stringing a line from the FiOS box to the router anyway), & good luck getting them to set up a technician to come out even if you swear to a supervisor that you aren't worried about being charged for the site visit.
If you're talking about hooking a 2nd router to the FiOS router so that a) you can have more than 4 hardwired devices connected, or b) for whatever reason you can't use wireless on the other devices, then check the 2nd router's manual about connecting its WAN jack to another router's Ethernet jack to extend the Internet connection. Be advised, however, that FiOS tech support will NOT help you troubleshoot if you run into issues: their tech support, per the Terms of Service, is limited to FiOS-provided equipment only, & they don't support a) using a non-FiOS router in place of the FiOS router or b) hooking other routers up to the FiOS router for additional connections.
And in case you're wondering, I spent just over 2 years working for a 3rd-party company that provided over 90% of the Verizon FiOS technical support agents, which means I'm very familiar with the technical support steps (including the dreaded "unplug the Power Supply for your FiOS box, wait 30 seconds, then plug it back in") & what they will & won't troubleshoot.