Generating the mesh using points

Select Mesh->Element type->Points. Select volume number 1 and press ESC.
Select Mesh->Generate mesh.
A window comes up asking whether the previous mesh should be eliminated. Click Yes.
Another window appears in which to enter the desired element size. Leave the default value unaltered and click OK. The result is a mesh as illustrated, where volume number 1 is meshed using 'point elements' with only 1-node. (Note that in render flat or smooth visualization mode the nodes may not appear in the screen depending on visualization properties. Set render normal mode to see them).

Generating a mesh on a volume using points.

GiD user manual