There is a turn type valve at the bottom of the faucet connector, where the water drains out. When you are ready to fill, you close the valve and presto! Water flowith into the tank. Add all of your water conditioner directly to the tank BEFORE filling.
Thats not necessary. You only need to add enough for the water your replacing. Adding it to your tank is fine because because when you add the water it will move around the tank so much it will mix up quite well.
The dechlorinator chemicals work VERY quickly. All of the chlorine/chloramine will be deactivated just about as quickly as you can fill the tank. Not a problem at all to fill directly from the tap with the water conditioner already in the tank.