There is two ways to get a screenshot of your poll. The first way allows for you to do a screenshot one poll at a time and the other way allows you to screenshot up to 10 polls at once.
1) When you click into your poll, click on Export icon between "Edit" and "Delete" at the bottom-right hand side of the screen. Under this menu there should be an option for "Screenshot." This will create an image of your poll results that you can save and insert directly into your slideshow.
2) Place a checkmark next to the polls you would like to get a screenshot, then click on the Download button and then Screenshot. This will create a zip file of all of your selected screenshots into a picture for you to save. You can only do screenshots of 10 polls at a time.