When trying to install Shapely on my Windows 64bit computer, I cannot get the GEOS library to work. 
So far, I have run the OSGeo4W installer from which I installed GDAL (I believe the geos library is included in that package). After that, I checked and I have geos_c.dll on my C:\OSGeo4W\bin directory, but either I have missed some configuration steps or the library does not work.
I need Shapely to work, so I also ran pip install shapely after  installing GDAL, and it apparently worked (although it could not find the C library for GEOS). 
In my code, I can import Shapely, but when I try to use it, I get an error telling me "geos.dll" is not found.
Any help with this will be very appreciated. Thanks!
I tried the method of @jozef but failed even I imported the folder to the path.
A straightforward solution: add geos_c.dll, geos.dll to the library folder of your python environment. Then it works.
Python, GEOS and Shapely on Windows 64