As you can save items like pictures, videos on facebook app. You can also manage them by creating separate collection / folder in facebook app. SO first go to the Saved Section.
In saved items, at the top you can see a button named as Create Collection. Click on it..
It will ask you to enter name for your collection.
Now you need to enter the name as you like. For example here i am entering "Funny Collection"..
Finally you can see that your collection is created..