How to load DLL using Iron python - .NET?

How to load DLL using Iron python - .NET?

I wrote the simplest DLL using C# and copied it to the desktop. Now I
wanted to load the DLL in order to see that I can use the API but I get
some errors:
the code I used:
import clr
clr.AddReferenceToFile("C:\Desktop\DLLTest.dll")
I get this error :
Traceback (most recent call last): File "", line 1, in ValueError:
filenames must not contain full paths, first add the path to sys.path
what is needed to be added to sys path? why? thanks!!!