grass is a material surface - usually on a mesh or slab - look for LS grass green in the material list.
same with carpet unless you have a carpet free standing - then make a thin slab and put your carpet material on it.
You need a proper license to not print with the DEMO warning.
There's a dimension tool in the toolbar.
You click on spots and it does the job.
Do you have any tutorials or manual?
Dwight Atkinson