How to brew green tea with japanese tea bags?

I'm so sorry for this ignorant question but I have never drank tea in my life. I saw a box of japanese tea bags in my pantry and decided to have a taste. I poured hot water in a mug and then put the tea bag in. When I sipped it, it tasted like nothing, just plain water but smelled nice and that's it. I thought it was supposed to taste bitter or something. And is there a way for it to taste sweeter or more appealing?