How to integrate with this plugin??

Hello, I was trying to use a plugin to able registration/login in model popup. They provide some class to add to show the popup. I can add this class to the menu. But how to integrate with this plugin for the login widget?? Please help if possible. my blog address if https://www.civilenggnotes.in

Here is the plugin link: https://wordpress.org/plugins/ajax-login-and-registration-modal-popup/