Adding a caption below a photo

[bxgti4x4]

I have PSP 2020 installed on my PC but it is about a year since I used it. I would therefore be very grateful if someone could remind me how I managed to get the yellow caption shape below the attached photo. I would like to repeat the process with other photos but, whenever I try to extend a shape layer below the photo, it will not move. I am missing a vital step and would be grateful if someone could remind me.

[LeviFiction]

Resize the Canvas.

Image -> Canvas Resize

Then add height to the image and make sure to press the Center Top button on the alignment so that only the bottom of the image is extended. While it does help to be exact in how much space you'll need, if you're not sure how big the caption will be, then extend the bottom of the canvas a lot and crop it once you have the look you want.

[bxgti4x4]

Thanks LeviFiction, that's great, thanks very much.
Kind regards
John