You do not always have to use bike lanes. That said, you should keep right and understand that cannot legally ride your bicycle everywhere.
North Carolina, like every other state, classifies bicycles as vehicles. This gives bike riders the legal right to use almost all roads and streets. It also makes bike riders responsible for following all traffic laws (with an allowance for speed limits).
However, bicycles are not allowed on interstates or where signs inform riders that they cannot operate. Violating restrictions on bike use make it impossible for riders to collect on insurance claims filed against drivers even when drivers are more at fault for crashes.