ID:2586745
 
(See the best response by Ter13.)
Code:turf
icon='turfs.dmi'
grass
icon_state="grass"

Problem description:
it doesn't recognize the turfs.dmi file that is on my left

What exactly do you mean by "doesn't recognize"? Do you get an error when you compile? Or is it not displaying correctly when you run it?
In response to Magicsofa
he says that the file could not be found
Then, you either have to create it (by selecting file -> new, then make sure you have the type set to icon file!) or there's some other issue like the name. Make sure the spelling in the code matches exactly, it's easy to create turf.dmi but then write turfs.dmi in the code by accident.
Best response
You may have directory searching turned off. If your turfs.dmi file is in a folder called "graphics", you will need to enter the path to the file: 'graphics/turfs.dmi'.

Otherwise, you can turn on FILE_DIR setting via Build->Preferences