Don't give up just yet. You've obviously been thrown in at the deep end through no fault of your own. You'll find, once you get to grips with the basics, that keeping fish is such a rewarding hobby. In fact, we have a famous saying in this hobby. It's not about keeping fish, it's about keeping WATER! Look after your water and the rest looks after itself. That's why, at this very early stage, the API liquid test kit is going to be your best friend. Once you find out what your parameters are, that is your water chemistry, then you tailor your water changes accordingly.
As well as the test kit, other essentials are dechlorinator and, as mentioned, a python water changer. This beats the bucket method hands down. Dechlorinator, or Seachem Prime as it's better known, neutralises the chlorine in your tap water. Chlorine is not good for your system at all. Look for a used, larger tank in your local ads, you can get some good deals on there.
Also, you need to research "the aquarium nitrogen cycle". This is the natural process that allows us all to keep fish in the first place, and you will then realise the importance of regular water changes once you have an understanding of this process.
And never ever feel uncomfortable about coming on asking basic questions. We all started out as newbies at one point. We will be glad to point you in the right direction in your efforts to look after your oscar, the poor thing deserves it.