thank you for your help!

when I select create TIN from scratch and layout a rectangular field it is subdivided into squares but there are no triangles within. What step am I missing. Thank you for helping.

I may be jumping the gun or exceeding my beginner comprehension level but I wish to construct a 3d site with a few known spot elevations across the front of a residence in order to propose/design an entry sequence from the curb to the front door. I just purchased SketchUp Pro. The longest dimension(some 275 feet) is paralell to the street and the shortest(150 feet) from curb to rear property line. The maximum vertical change across the long dimension is 4 feet and the elevation change(s) are consistent and gradual. I assume that constructing a TIN with the scratch tool is the way to proceed? Assuming this is the correct approach is there a step by step tutorial that is best? Thanks you for your insights and expertise.