Open single image in pop up window Not full page

Hi, I’m new here and have searched forums for this but can’t figure it out.
I do not know how to write code.

When I post a single image to a post and click on it, it opens full page and the blog interface is gone.
One must then click the Back Arrow on the Browser to get back to blog.
How do I just have picture Enlarged in a pop up window instead, when clicked?

Thank you