Help Cache/space issue

[Kracov]

Hello all. I finally got my first smartphone, a Samsung Nexus S 4G. I think it has Android 4.4. The issue I'm having is that I don't know how to clear the cache or storage. I get errors when trying to install apps on the Play store. I tried 2 cleaner apps. Didn't free up much space. I'm using up about 90%, even though I don't think my apps are using that much space. Anyway, I was messing around with google settings as well, and now my wifi signal is white instead of blue/green. I can access the internet but it still worries me about data usage. I hope someone can help me free up the space or clear cache.