DLL plugins unsupported for Android Application Building

I am developing an Android application in VR using Unity, I wrote some functions in C++ and imported that as DLL file in my Unity project. The DLL was imported successfully when it was running on Windows. The main problem came into picture when I was building the same for my android device, Unity had built some app but it crashed when I installed it on my phone.

I made some research to find out what was wrong, and I found this answer (http://answers.unity3d.com/questions/722496/how-can-i-include-a-c-dll-in-the-apk-file.html). Someone said that I need to make a .so file. I made that using NDK on Android Studio.

Can someone help me with how to import that .so file in a C# Script on Unity?