How to use a custom cordova plugin in ionic 3.x?

Hi guys,
I need a help!!!
I have a custom cordoba plugin and I am not able to use it in ionic 3.3, in version 2 I was just declaring the window variable and calling my plugin via window.MyPlugin. Does anyone know how I can use this new version of ionic?
I realized that the native plugins besides using “cordova plugin add” is used a npm install ‘@ ionic-native / xxxx’ and a folder is created in node_modules.

Nothing changed in handling of Cordova plugins from Ionic 2 to Ionic 3.