Two-thirds the way dow nthe Collection Summary screen you should see this
Unopened Material
You have 0 unopened items listed.
One thing you may need to look for is which Collection you are on. When initially going to the Summary screen it defaults to All Collections. With that screen you will not see the Add Items line. Using the dropdown you'll need to go to an actual collection (Main Collection or whichever ones you may have). Once you select a collection those option which a) appear and b) be the default as you move between sets.
When the sky is coming down
When you feel like you're going to drown
When you know the end is all that you've been looking for
When the pain is too much to bear
When there's no one who will care