Step One: Select the proper tool

Click on 'Marketing' link under the 'Website' heading of the Control Panel menu. 

Step Two: Select new arrival notification tool

Click on the 'New Arrival Notification' section to open its settings page.

Step Three: Open the 'Advanced' tab

Click on the 'ADVANCED' tab.

Step Four: Make updates

Next to 'Optin New Accounts' label, click the 'YES' button.

Note: If "Yes," new users are automatically opted in for all categories.                                                                                                                                                

Step Five: Don't forget to save

When you are finished, scroll up/down and click the 'SAVE' button.