When your project requires a transparent background image file for printing on merchandise (t-shirts, mugs) for instance, you can make one in PicMonkey and then download to your computer for using elsewhere. When you export your transparent-background image as a PNG, this file format maintains the background transparency.
Steps for creating a text-only PNG for printing:
With your blank canvas in the PicMonkey editor, open the Layers palette.
Select "Convert to layer" on the Color Background layer.
Now you have a new layer called "Color layer". Select and delete it.
Your canvas is now transparent.
Add your text to the canvas and adjust as desired.
Click Download and export your file to your computer as a PNG.