Making other tags and objects flow around a popup image


So I have created a type of popup-image which pops up on an onclick. But the thing is this image pops up over the background image and the existing text. I want to know how I can make things flow around this image when it pops up?

So for example I want to make text and buttons in this page, which is an about-html-page, flow around the pop up when it appears. But I don’t want the background-image cover-image to wrap/flow around the popup. Only the text and buttons in the page if you know what I mean.