I have Ps Elements, which I believe is very similar to PS.
To add a comic strip like box, click on the shape selection tool, then on custom shape tool. There you have plenty of default shapes, including "thinking boxes", for example. You have always the option of drawing the box yourself. After that, you can choose the box style (colors, transparency, things like that). Then insert the text, by clicking on the text tool. Really easy. Don't know for sure if its the same on Ps, but explore the tools I mentioned.
Hope this helped. |