OneTime Premium offers you to upgrade a single poll. Check out the premium benefits on the Plans & Pricing page.
After you’ve bought the OneTime premium upgrade you’ll have to apply it to a poll of your choice. Your polls will now show a link to enable you to upgrade the poll. Click on the link if you are in the poll that you wish to upgrade.
When you have upgraded your poll it will show a "premium" banner above the poll’s title in the organizer’s view. The guests won’t see a change.
In the poll’s settings drop-down menu you’ll see all the Premium benefits enabled, like adding a cover image, or downloading the poll’s data.