Hi,I have known your question and try to help you out.
First,I do not recommend you to copy plugin content manually,because for different versions,it doesn't work at all.
For now,you have copied our plugin files into your project root file.
The steps below may help you a lot:
1.Right clicking YOURPROJECT.uproject,and generate Visual Studio file.In your project solution,I really suggest you to use UnrealVS(../../Engine/Extras/UnrealVS) for hot-reloading,which is provided by EpicGames.
2.Try to use VisualStudio to launch your project instead opening it directly.
3.In UE Editor->Content Browser->View Options,make sure you have checked "Show Plugin Content".