A great use of the Form Builder is creating forms for contests, especially using the submissions limit and expiration date settings. A great place to start with setting up a Contest Entry form is to use the contest entry template available in your form builder.
To start, click on the Forms icon and then click on form builder. From there, click on new form and select contest entry from the list provided.
This will add a form with certain fields already added. You can change the text to fit the particular contest you're running and add more fields if needed.
You can also set a submissions limit (if the contest is only good for a certain number of entrants) and/or an expiration date (if your contest is only running for a certain amount of time). To access these controls, click on the gear icon toward the top right and then click on settings. On the Settings page, you can enter your submissions limit and expiration date.
Make sure to click on save changes at the bottom of the page after these have been entered.
Below is an example of what your contest entry form could look like, with both an expiration date and the number of submissions still available.