The first signs of your mushrooms emerging is called "pinning", where white clusters of pins will form through the holes in the bag.
Keep them well hydrated with a spray bottle at least 5 times a day, just like you've been doing to increase the humidity around the bag before pinning.
After a few days, you will begin to recognize the blue oyster mushroom shape!
Harvest when the caps are a good size (at least an inch across), and the edges of the caps are still turned downward.
If you wait too long to harvest, the caps will thin and flip upward, as the mushroom prepares to drop it's spores (and that's a pretty messy process indoors).
The clusters will preserve well in a container in the refrigerator for a week or more, so better to harvest them at their peak.
Grab the base of the entire cluster and twist. There is a YouTube video on our YouTube channel of a demonstration of harvesting from a Greenwood Farm Kit.