I just set up my tank for my oscars, when i do a water change, do i have to put the chemicals in the 5 gal bucket that is holding the change water? And then have it tested before I do the change.

Welcome to the site

Is your tank cycled? I'm doubtful from what you've just said about just setting it up. Anyway, to answer your question, I assume we are talking about a water conditioner to remove chlorine? If you are using buckets to replace water then you can work out how much water you are taking out and then work out how much water conditioner you need. You can then add it to each bucket if you want. You don't need to test the water as most water conditioners remove chlorine instantly. Alternatively, put some water conditioner straight in your tank and then add your water.

The easiest way to refill your tank is using a hose pipe attached straight to your tap. Again, add the water conditioner into the tank as the water goes in, just before. I been doing it like this for years.

When you say JUST set up the tank for oscars, what do you mean? do you have oscars in the tank already?
or are you cycling the tank first?

please check out the "how to cycle a tank"link on the home page and the "nitrogen cycle" post in the chemistry section...then tell us how far allong you are ...this will help us advise you exactly on your next actions..hope this helps

you've been covered by the guys/gals.

all i can say for the meantime is welcome to the site