(And yes, it is funny that my bird food tray has a cat hunting a toy mouse.
What can I say? Cute, and it has been in the family, so many memories.)
Wrapping the top of the food dish in paper is easy, and provides a little enrichment with every meal. Decide what method is best to attach the paper to the dish considering your parrot. If your dish fits in a ring, which is the easiest, you can just tuck the paper in the edge of the ring. If not, I have used both rubber bands as well as cotton kitchen twine. In this case, for Clementine, I am using a rubber band as that works well and is safe with her.
Get a supply of whatever paper you plan to use and keep that next to the bird dishes so it is on hand. After filling the dish, or dishes, take a piece of paper the size you need and tie or wrap, etc, it on.
In the beginning, you can just put a strip of paper around the edge, or across the middle, so most of the dish is uncovered. Gradually cover more of the dish, until it is all covered. In this example, I still have a small hole for Clementine as she is still learning about foraging.
Once a piece of paper is mastered, you can try more layers, or even thin cardboard for larger beaks. Use your imagination!