For a video tutorial, check out:  

Step 1 - Navigate to your form's dashboard, and click Periods under the Data Collection and Form Lifecycle header. 

Step 2 - Click + Add New Period near the top of the Periods page.

Step 3 - On the New Period page, a selection of period properties will be available for you to enter.

The editable fields are as follows:

• Name: The name associated with the period.
  • NOTE: This is the only required field.
    
    
• Enabled: If unchecked, the period will be be turned off and rendered inaccessible to the rest of the form.
  
  
• User can create multiple forms in a single period: Determines whether or not users can fill out additional form responses within the period after making their initial submission.
  
  
• Description: The period's description displayed in the Periods menu.
  
  
• Start Date and End Date: The dates marking the beginning and end of the period's "availability." A user will not be able to access a form before its current period's Start Date, nor after its End Date. Leaving both fields empty will make the period available to users at all times.

When you are finished, click the Save button at the bottom of the page to return to the Periods menu.

Step 4 - To set the new period as the current period, click the settings gear next to the period's listing...

...and select Set as Current from the dropdown menu.

For more FormBuilder tutorials, visit FormBuilder - Homepage.