To get started collecting email addresses for a mailing list or newsletter, all you need to do is add a form field checkbox for "Email Opt-In". Go to the Woobox dashboard, select the promotion in question and click Customize on the left hand side. Click the Form Field section on the Entry page, then click +Add Form Field from the left navigation. From the popup, select 'Email Opt-In'. Set the label to anything you'd like, and set the default to checked or not. Finally, click add.
From then on, every time a user enters your promotion, they may choose to be opted-in to emails. Once you have started collecting this data, all you need to do is export all of your user data to a spreadsheet file.
Where do I get the entrant data?
Simply go to the Entries page in your offer dashboard (you'll see this in the left-hand sidebar), and click the Export link in the top right of the entries summary table (the table on that page will show the first 500 entries). Clicking Export will download a CSV data file which can be opened in Excel, Google Docs, or any other spreadsheet application. Alternatively, you can go to Export -> Download Exports for the Entries CSV and Stats.
How do I identify the form input associated with each column?
You will be looking for the field titled custom_#, where # is the number of the field type 'emailoptin'. To find this number, click the Form Fields section on the Entry page and then select Code in the left navigation and select "Edit HTML". In the HTML of the Form, you will see field IDs in this format name: custom_#. Find the name associated with the field 'emailoptin'. This is how the column on the export will be labeled.
Below this field in the spreadsheet, users who have this box checked will have a value of "on". You can then sort the sheet by this field to show all users in a row who have opted in. Depending on your program, you can then export all of those emails to be fed to the mailing list of your choice. If you are using direct email integration, these users will be automatically added to the mailing list.