Where to Find Text Bubbles

I seen this in E.R Gurney’s story, Under You, where she included text bubbles every time the characters in her story would text on the phone. That is very cool, and I would like to do that in my story. So how would I be able to find text bubbles?

You would have to make the overlays of the text messages

How would I be able to do that?

You would have to create them on some sort of software

Like pixel editor . Com