Okay, you’ve poured the water. Now firmly close the cap or lid. Give it a little twist—not Hulk-strong, but enough that it won’t pop open when you tilt the iron later. A loose cap is a recipe for a surprise puddle on your nice shirt, and that shirt has been through enough.
If your cap has a little click sound, that’s the sound of success. If it doesn’t click, just make sure it’s snug. We’re not landing a spaceship here.