You set them up in the config.txt file, like this:
node1.name=Node One # name to display in the web interface
node1.rpchost=127.0.0.1 # IP address of MultiChain node
node1.rpcport=12345 # usually default-rpc-port from params.dat
node1.rpcuser=multichainrpc # username for RPC from multichain.conf
node1.rpcpassword=mnBh8aHp4mun... # password for RPC from multichain.conf
node2.name=Default # name to display in the web interface
node2.rpchost=127.0.0.1 # IP address of MultiChain node
...
The node1 and node2 strings can be anything alphanumeric, but need to be used consistently within each group.