It is good to let the tank sit for 24 hours just to let everything settle. If you are keeping an uncycled tank, then you would have to change the water periodically (I'm not sure how often in a 10 gal, does anyone know?)
If you want to cycle the tank so you don't have to change the water quite as often, then you can use the above link on the nitrogen cycle. I cycled my tank using a kit, and it only took a week before the cycle stabilized (which was surprising, and pretty awesome). I kept my fish in a small betta bowl during that time and changed his water every couple of days. It's good if you already have the fish and you want to get the cycle going immediately. Options 1-3 in the link above are really better if you haven't bought your fish yet, or if you have another suitable habitat for him. I recommend something like this cycling kit
to test if it's working because these are what I use. However, other brands are just as good. This is just to give you an idea.
You could also add live plants to help absorb the Nitrates and Ammonia, but don't worry about that just now. Just a fun idea for the future! :)
Cycling is, in my experience, the scariest part of being a new fishkeeper. When I first started keeping fish, I left my tank uncycled for a good three months because I didn't know where to begin (/thanks the forum), but it turns out that it's alot easier than we make it sound. Have fun! :D