How to add "Share Icon" to nav menu

Site URL: https://atmos.art

Hi,

I would like to add a share button exactly like the one on this website, including the pop up box that displays when it is clicked. How can I do this? I noticed that when I hover over the icon, it displays a link in the bottom left corner related to javascript if that helps. Screenshot attached for reference

https://natcoalson.com/

Please note that my nav menu has disappeared for some reason and I am in the process of trying to fix this.

Thanks

I think you can add a 3rd party share, it will appears on left or right of site, then we can use code to hide it + add icon to nav + make when click icon >> show this share feature.

For example: Addthis, Shareaholic