Do you have a design template for the background? If so, you can edit the Slide Master and insert the image there as a background image for all slides. See here:
Learn how to add slide masters to your presentation.
support.microsoft.com
This will allow you to work with your design but still add text and stuff via powerpoint.
The idea with a screenshot is also a great one. Or you could download the canva design as a png or even as a pdf. The button for it should be in the top right, you can save it from there.
If you just want to print the slides, why not copy and paste the canva pictures into a word and then print them?