To add a survey, select "Create a survey" from the Add Content screen. Surveys can ask for up to three fields of information, name, email and a free text question that you can define. You don't have to use all the fields so may, for example, just ask participants for their name and email address.
Here's a short video walking you through Surveys.
There is some overlap between surveys and requiring attendees to provide information when joining a Zeeting (you can learn more about the latter here). Use a survey when you do not want to make entering information the first thing that happens when a participant joins or if you want to also ask for additional information such as feedback on your presentation.