How do you add nodes on a map?

I’m working on a map that my friend is helping me with and he tells me to add nodes, specifically ground nodes, on a map because it’s going to be zombie-themed. I’m a really noob mapper and was curius on how to add nodes on a map, nodes I’m assuming are paths for npc’s to traverse on. Anyone know the command or how to displace them? A specific walk through would be cool because I admit that I’m s noob at mapping.

I thought you just placed a shit load of Hint nodes.

Did you really not see this?
http://www.facepunch.com/showthread.php?t=972022

Try this out;

Just place info_nodes all round where your zombies are going to walk.
Place climb nodes and info_node_air’s at possible jumping points for fast zombies.