Slide in menu for both mobile and desktop

Thanks to your awesome team, I have been able to make much progress making my FIRST professional site and my first ever community. It looks like this

When the notification icon is clicked, the user is taken to alerts page. I want to change this. When the notification icon is clicked I want a menu to slide in. Like this:

I want the same thing to happen on mobile. I have no idea how to accomplish these results. Please help me, this is very important for my business.