This is not a real popup. It's a jquery lightbox. If you include jquery and google 'lightbox' you'll find lots of examples, but overall if you're new to web programming, I'd suggest you learn javascript AFTER you've learned ASP.NET MVC. If you're learning something else, abandon it and learn ASP.NET MVC.
Here[
^] is the site for the lightbox plug in. You should be able to just copy the code from the site ( you will need to include the right libraries, and probably download them ). It doesn't need any sort of server side code, you can do it in pure HTML.