First off, I need to make sure if I have identified the right tank (duh, I know !) I read on another post which says it's the one with the green cap, but green cap is nowhere to be found under my hood. So I looked at some pix of others' car and saw this one (I have to borrow from FineExampl, hope he's okay with it)

If that tank next to the battery indeed is the power steering fluid tank, the second question is how do we know if there's a leak? When I checked, the fluid level is at the level where you can hardly see from the outside, so very low, and the original signal to this checking was the moaning from the steering wheels on turns. Should I just fill it up and it's done with or is this signal to some leak? I noticed there's no fluid on the ground after leaving or anything like that.
I've troubled with these litle things that I find days after days with this car after 1 month owning it. So please don't tell me I need to change the power steering pump, or some PITA things. (If you really have to, pls say something inexpensive) J/K. I'm looking to hear some news !