You need to top up the PSF (Power Steering Fluid). Its in the engine bay, pop the hood and look for small canister near engine saying PSF or having icon of steering on top.
It shud have small dipstick to see the level, check if its low. It shud be properly FULL. While pouring more fluid turn the steering full left and add, then do full right and add, this will eliminate having any air bubbles in the line and fill the fluid fully.
Do this and im quite sure squeaking will go, if after few days it comes back then you have leak in power steering assembly or hoses or pump. Get it check and get it fixed asap, as its serious.