How do I make my post bigger or smaller?
It's only possible to change the size of your posts in the canvas format. If your padlet is in any of the other six formats you will not be able to manually resize your post.
In the canvas format, this is how to resize your padlet:
Non-touch devices: Hover the cursor on the edge of post. When the double-headed arrow displays, drag to adjust its size.

Touch devices: Pinch and zoom on the image!