You put the weed in a mason jar or other pressure/heat safe container, add 2 cups of water to the cooker and set it for 1 hour. It bakes the weed at 240 which is just about perfect for decarbing.
Here is a video showing the process. She goes 40 min, but I go an hour. Pretty good info from her.
Does this mean you could use them for brownies? Years ago in Oregon, I bought a big bag of trimmings and rolled joints and made brownies, they all got you high (not like buds, but a nice 'party ’ high). Were those 'sugar leaves around the bud? They didn’t appear to be ‘water’ or ‘fan’ leaves based on small size.
What a delightful, informative video - thanks!
It also taught me that an IP doesn’t get hot enough to convert the CBD. I didn’t even know CBD needed any conversion from raw.
So far, everything I learn leads to another question! 
I did not know that before this video either.
I use the leaves and add some buds to make 'magic butter, purchased the butter machine. My first effort made 900grms with organic coconut oil. I did not put them in oven as instructed by recipe. Added 2oz leaf and buds, dried.
I am not about getting high, just some relief for chronic back and now hip pain. That will last me about 8 mths, taking teaspoon morning and evening.
Does not stop pain but eases somewhat and I get 8hrs sleep.
Next time I will remember to 'bake leaves. That was my first effort.
You can decarb cannabis in a 250*F oven, wrapped in alum foil, for ~30-45 min.
Thank you, I think I had a ‘seniors moment’ when doing this 1st time, but is helping me.