When you first click Create a new poll, BallotBox will show you what you can configure. It will look something like this:
As one of the steps, you will need to create a questionnaire for the poll. You do that on the Questions tab. When you first get to that tab, it will look like this:
If you have a poll that you ran in the past, and its questionnaire would be a good starting point, you can import it into your new poll. You do that by clicking the Import button that is next to the first tip (the first light bulb icon).
In the dialog box that appears, use the From Previous Poll pull down menu to select the questionnaire you'd like to start from.