chrome extension Select dom element on click

Question

i created a chrom extension that opens on a side panel following this How to make side panel in chrome extension?

i know that from the iframe i can access the parent DOM now i need to add a button to the extension that when clicked allows me to click on a dom element on the web page and get the content of that DOM element

my main use is to be able to grab content from a web page e.g a title but i have no idea from where to start