You cannot use JSON RPC until you have connected your second node to the first node. When you run the above mentioned code on your second node, it will show your nodes address. Take that address and use it to grant send/receive/mine permissions from the first node.
Once granted, connect to the first node from the second with 'multichaind chainname --daemon'
Then decide which server you want to use for the JSON RPC calls. Checkout '~./multichain/chainname/multichain.conf && params.dat'
Be sure to enable RPC connections from non-localhost. Then take your RPC username and password from one of those docs, you will need it to connect from.
Checkout my explorer (work in progress) for my Multichain-based blockchain. Check app/services/bitcoin_rpc.rb for connection info with RPC. Then check app/controllers/sessions_controller.rb for how the RPC calls are made.
http://github.com/padchain/explorer
Hope this helps!