To create a poll you need to first set up your template:
Navigate to the Templates tab and and select the Polling tab (all of your poll templates will live in this tab).
Select "+ New Template" and add a name in the Description field.
Select the Anti-Alias and High-Resolution options (this ensures any images will look great in your email!)
Select the canvas to change the background color and size.
If you want to have your poll/vote numbers overlaid on images, then follow the step to add background images. If you just want a solid color background, proceed to add your voting.