Hello everyone,
So my problem is that when i press on any kind of item an enlarged preview of it appears, but I want to do is to make a flash file to pop up in the same way(I've uploaded a picture of it.). Or maybe if it's possible to make a component appear in iframe ( for example: index.php?option=com_flippingbook&view=book&id=1 ).

I'll appreciate any kind of help :)

Use RokBox www.rockettheme.com/extensions-joomla/rokbox

I installed it, but how to integrate it into K2?

Basically: you can use {rokbox...}link{/rokbox} or <a rel="rokbox" href="/...">example</a> code in your article.
Read Documentation how it works first at their site. It's very detailed.

But there is no place for me to write that link(attachment)