The bell is reverting back to a flat surface once I hit edit mode. I've redone the previous step a couple of times, just in case I missed something but still the same result once I hit edit mode. Is there something that I'm missing?
That's because you have the "Basis" shapekey selected. If you switch to the "Cloth" shapkey, you'll be able to edit as expected.
You can see this at 5:00 in the video.
Yep, that was it. Thanks Kent!