"Second step: These changes need to be made in Skyrim prefs ini

bfloatpointrendertarget=1
bTreesReceiveShadows=1
bDrawLandShadows=1
bShadowsOnGrass=1"

The ReadMe doesn't specify which categories to add them in (e.g. [Grass] [Shadows] [Clouds]).

You dont add them, they should already be in the ini and just need to match what he says.

You can find them easily by clicking at the top of the in file and then press CTRL + F and a search box will pop up. Type out the ini line you looking for and it should take you to it.