I know this is a simple beginner question, but i forgot how to do it.

so i m reaching out here for someone who can hopefully give me the simple help i need...
i am trying to post a pop under code in my footer to pop up when someone clicks on the link, to have one of my webcam whitelabel sites pop up, but i have no clue how to do it.
Everything i find always has a button associated with it, how do i do it without the button, and with just the on click?
thanks.