A very simple example can be found here:
sample_file.mw. You will need to download the release 64-bit shared library for windows from sourceforge or the development version of the shared library from the snapshot server.
Place the downloaded DLL in c:\CoolProp and rename to CoolProp_x64.dll
On other platforms, the protocol should be more or less the same. Download a DLL appropriate to the version of Maple you are using from sourceforge or the development version from the nightly snapshots. You will probably need to change the path to the shared library in the Maple file, but aside from that, it should work fine. File an issue at github issues if that is not the case.
A more in-depth example has been put together by the Maple Enginers:
Analysis of a Refrigeration Cycle with CoolProp.mw