The Badlands node sits at the far south edge of the map, well away from the entrance.
Where it is
The Badlands. The marked map is on the location page: The Badlands.
Getting it
No trick. Get to the south end of the map and use the node. Mind the company out there.
Melding
Stand within three squares of the node and use it. The bond raises your maximum mana by three points plus one for every ten points of Mysticism above five, so between three and eight depending on how mystical you are. You can bond with each node once, and the game will list the ones you hold if you ask.
This node can be drained by the Xeochicatl. See Nodes for what happens when one is attacked.