To load the API (if you saved it as "RNP"), just use:
os.loadAPI("RNP")
RNP.start()
To broadcast data:
RNP.broadcast(string type, string src, string dest, dat)
Where type is the Lua type of the data, src is the sender of the file (use RNP.name if unsure), dest is the destination computer's RNP.name, and dat is the data sent
To receive messages:
RNP.receive(type)
Where type is the type of message received. It returns
{ string type, string source, string dest, table step, dat }
Step lists all nodes the message was sent through. If a node is already on the step list it doesn't forward the packet.