It's pretty straight forward. Just place it on plan and have a play with the settings! Here is a quick guide to the parameters. Feel free to add any corrections and clarifications - this is just based on my understanding.
Grid Size.
'Number of control points'
Controls the number of hotspots available for adjustment. More hotspots, more control.
'Grid size'
Controls the fineness of the surface mesh. More divisions gives you a smoother surface.
'Show grid'
Tickbox turns the display of the surface grid lines on or off. Affects 3d only. Also allows adjustment of pen.
Appearance.
'3d representation'
Changes the display from wireframe to solid.
'Grid type
>Surface - A simple plane. Can't be used for SEO.
>Thickness - Gives you a solid body with uniform thickness. The sides will always try to remain perpendicular to the top surface. Can be used for SEO.
>Base level - Similar to the normal mesh tool, creates a solid body with vertical sides that extends to the base level dimension. The dimension specifies the height at which base starts from 0.000.
>Double sided - Allows independent manipulation of both top and bottom surfaces.
'Offset'
Adds extra height to the vertical sides.
'Interpolation Method'
I believe 'Linear' interpolates between two points so giving sharper edges, and 'Cubic' four points - smoother.
'Edge Visibility'
Turns the four main edges on or off. Affects both 2d and 3d.
Materials
Top, side and bottom materials.
Sides in rendering
Corrects texture glitches to all faces. Leave unticked for smooth.
Operations
'Rotation around X / Y axis'
Tilts mesh over.
'Scale in X / Y / Z direction'
multiplies all relevant coordinates by this amount. To reverse an action, enter in the inverse amount first put in; e.g. enter 2.0 to double the size, 0.5 to return.
'Presets'
Creates a preset shape either of a saddle, a paraboloidic tube, or a vault.
2D features in parameter list
'2d view'
Specifies either normal plan view, or a cut horizontal section at 0.000 level.
'Show grid in plan'
Controls the 2d view of the surface grid regardless of the grid display in 3d.
Usage -
Start simple with low number of control points. Add extra points later as location of correct hotspots in 3d view quickly becomes difficult.
Try stretching XY positions on plan, then adjust height in 3d.
Editable hotspots are in vertical pairs in 3d. Lower hotspot controls XY position, upper controls height. They are labeled to avoid confusion.
Stretching it to extreme proportions causes glitches on surface.
Holes can be punched through with SEO. Geometry can also be trimmed to the mesh using SEO, except when set to wireframe ('net') or 'surface'.
Hope that helps!