If you're connecting it directly to the Mac you'll need a cross-over cable. Otherwise, if you have a router, connect it there.

On the Karma, drill down to the Network settings menu, make sure DHCP is enabled. In the "Current Lease" menu you'll see the current IP address of the Karma. In the password menu set the password if there isn't already set. You'll need this password to access the Karma from the network. Then fire up RMML and synch away.