Running MSMPI in CLion (Windows)

Question

I am a newbie at MPI. I am running my very first hello-world program in Win10 using Clion but I failed. I have searched for many sources on how to modify my cmakelist. The closest I found was an official Microsoft-MPI instruction that shows how to run the program on VSCode: Microsoft-MPI-example

I attempt to modify it on CLion, so I came up with a cmake file like this:

cmake_minimum_required(VERSION 3.14)
project(A C)

include_directories(${MSMPI_INC})
find_package(MPI REQUIRED)

add_executable(A mpi_hello.c)

This is a simple one, not including mpiicc yet. (I attempt to use gcc for compiling instead)

Question is the configuration failed:

-- Could NOT find MPI_C (missing: MPI_C_HEADER_DIR MPI_C_WORKS) 
CMake Error at D:/CLion 2019.2.2/bin/cmake/win/share/cmake-3.14/Modules/FindPackageHandleStandardArgs.cmake:137 (message):
  Could NOT find MPI (missing: MPI_C_FOUND)
Call Stack (most recent call first):
  D:/CLion 2019.2.2/bin/cmake/win/share/cmake-3.14/Modules/FindPackageHandleStandardArgs.cmake:378 (_FPHSA_FAILURE_MESSAGE)
  D:/CLion 2019.2.2/bin/cmake/win/share/cmake-3.14/Modules/FindMPI.cmake:1672 (find_package_handle_standard_args)
  CMakeLists.txt:5 (find_package)


-- Configuring incomplete, errors occurred!

What do I need to do to correctly include mpi.h as an external library? Was it wrong to use MSMPI_INC (which is, of course, the environment variable) in the cmake file?