How am I supposed to compile this repository into a .dll file?

https://github.com/SaltBlocks/IMXlib

This is the dllmain.cpp of the repository:

// dllmain.cpp : Defines the entry point for the DLL application.
#include "pch.h"

BOOL APIENTRY DllMain( HMODULE hModule,
                       DWORD  ul_reason_for_call,
                       LPVOID lpReserved
                     )
{
    switch (ul_reason_for_call)
    {
    case DLL_PROCESS_ATTACH:
    case DLL_THREAD_ATTACH:
    case DLL_THREAD_DETACH:
    case DLL_PROCESS_DETACH:
        break;
    }
    return TRUE;
}

I have no clue what I do need to set up to compile this repository.

I’m using Microsoft Visual Studio.

It says in a pop up window “Please select a valid startup item”.

I don’t know how to select it.