I have just started working with Blender and have run into a problem: I'd like to add a plane to a side of an object, but I don't know how to do it since it has curved edges, is there any way to add a plane based on the nodes I have selected, or do I have to do something else? Grateful for any help!
As Batfinger already said the points on the mesh are called Vertices and not Nodes. Nodes are a completely different sphere of blender which includes stuff like materials and compositing.
As for you question, selecting the Vertices and pressing F will fill in the faces.