When you setup the node, just specify one browser. The grid will automatically redirect the test execution commands to that particular node. No other setup is really required.
Say you have a grid server and 3 nodes. One node is hosting Firefox, another one Chrome, and the last one Internet Explorer. Below will be your setup.
java -jar selenium-standalone-server.jar -role hub
And node 1 configuration (chrome)
java -jar selenium-standalone-server.jar -role webdriver hub http://<grid_ip>:<grid_port>/wd/hub -browser browserName=chrome
Same way, you can start node with -browser argument and specify your browser.