Lightbox style plugins not opening until i open image page

On my website, which is NOT currently live, I am unable to make various lightbox plugins work the way I’d like.
on posts that have images scattered throughout (not necessarily in a gallery), clicking on the image always links the reader to the image’s URL. THEN, and only then, if the viewer clicks on the image, does it open in lightbox.
i’d like it to open in lightbox STRAIGHT from the post, with 1 click.
i’m new here. thanks for your help.