How can I add entrance animation to custom coded images?

One of the options with an image block is to give it an entrance animation from a list, eg fade in. Some of the images I'm using on my site are icons which I wanted to remain a fixed size (rather than being full-width and stacked on mobile), so I placed the images using HTML code rather than a standard image block. Unfortunately this means I can't animate them in the usual way.

Is there some code I can include in the HTML block that would give them entrance animations? I'm not interested in making entirely custom animations, I was happy with the default ones available on the image block editor panel.

Thanks

Hi. Can you share site url? We can help easier

I was actually looking for a similar answer to this question as well. I tried adding the following class to my div without any luck...

.combination-animation-site-default

I imagine I needed to do more than this but I haven't been able to find any answers.