Question about adding power steering fluid to my car

I've been noticing that my steering wheel has become a bit stiff. It also grinds a bit when i turn the wheel trying to park or make a U turn.I noticed that my power steering fluid was a bit low. Now I bought this car used. I don't know what fluid was used before, but I saw a universal synthetic fluid being sold at Walmart for cheap. Can I use this, and do I just add it in? Or should I completely flush it beforehand? via /r/cars http://ift.tt/2tzBfBz