border around individual photos

Here’s a link, by the way
https://mushroomfactor.com/

I’d like a border around any photo that doesn’t have a white background, which is most of them.

Okay, it looks like I have to answer my own question here:-) Which I’ve done, of sorts.

I figured out that if I delete the segment of code that comes with inserting the image, thus leaving just the <img class> segment, my border coding is applied.

But this gets tedious to manually have to do all the time. Is there a way to insert the image without it applying an ? Why does it do that?