You can create your collections first if you haven't already by following the steps here. Once you have your collections, you can follow the steps below to add the articles.
Point to the left-hand sections and click Content.
Once the list is expanded, click Collections.
Go to the collection you'd like the articles to be added to and click the Edit button.
Scroll down until you find the articles that are already in that collection.
Click the dropdown next to filter.
Select Unlicked Articles.
Now you can add the articles by simply clicking the Plus button.
Get stuck? Feel free to reach out to our support team using our live chat located at the bottom right corner of your Universal App dashboard or simply send an email to firstname.lastname@example.org