In order to protect a publication via a username and password login, first of all you must create a subscription group and add subscribers where the username and password will be entered for each user/subscriber. From here you will also be required to release the publication to the subscription which links the two together.
Once the above steps are complete, from the publication production screen, click on Settings - General from the publishing toolbar on the right:

You will be presented with the Settings menu which you must scroll down until the Subscription subheading is reached:
The various options and their functionality are outlined below:
- Subscription Required - Tick this box to enable the username and password access to your publication.
- "Remember me" when offline - When users login, ticking this option will present a tickbox to specify whether they would like to have the username and password remembered when offline access is required (therefore the publication will not need re-authenticating).
- Unprotected Pages - Unprotecting pages defines which pages the users who are not logged in can see before they are prompted to login with their credentials. For example, placing 5 unprotected pages at the start will allow five pages of your publication to be available for free/without login before navigating to the sixth page where the login prompt will appear.
- Official publish date - In relation to the subscription database, this is the date that the subscriptions will check against to see whether the publication is available within a given subscription/subscribers details. As default, this is set to the date that the publication node was created on YUDU (NOT when the publication was first published live).
- Ignore publication date when checking subscription validity - If selected then subscribers will have access to this publications while their subscription is active, and no access afterwards, regardless of whether this publication was published within their subscription period. If not selected, subscribers will always be able to access this publication provided the publication date is within their subscription dates.
- Use custom login prompts - As default the system will prompt for a username and password, however this may not apply to your subscriber/user base. For example, if you require a User ID and password, tick the box, enter a custom message in the login explanation and enter User ID in the user identifier field.
- Show subscribe button - The subscribe button appears in both the drop down options menu when viewing an publication and on the prompt when users are asked to login. this can be customised to display what is required, such as Purchase, or Buy Subscription, along with a custom URL, for example to the purchasing page of your website.
Upon completing the above options, navigate to the bottom of the page and hit Submit to ensure that your changes are saved.
To check your changes have been implemented, be sure to generate a preview link and test the options you have selected (unprotected pages, subscribe button, etc).