:) it's good to have two poland spring 1 gal bottle or a similar container on hand. One to fill up with new water. And one to fill with old water
Try to get the new water as close to tank temperature as possible. you can do this by adjusting warm water from the tap.
Add water conditioner to the new water in the 1st spare container.
siphon half the water out into the 2nd empty cotainer(you can use an airline for this)
Then add the new water from the 1st container (gently!)
For 100% changes. you can cup (or really gently net) the fish out of the tank and simply dump the water.
Make sure that your fish is kept in a container with a lid during the water change!
Also Make sure you have the conditioned water premixed before you dumped the old water so you know what temperature the new water should be. you can match temperature simply by feel.
add water then fish :)