I used sponges and rags in pans of water to raise the humidity the last 3 days. I also would mist the inside of the incubator through the vent holes if it started to drop below 65. Some people don't like the idea of the misting, but it worked well for me. Out of 10 eggs, 9 hatched, and the other one looked to have quit early on.
During lockdown you can take plastic tubing, like fish tank tubing, and run it through the vents into the water containers. I used a large syringe to replace the water when needed. When misting (if you do) or adding water, always use warm water, or at least the temp of the incubator.
It is the surface area of the water, not the depth, that will raise your humidity.