How to Upgrade?

Hello. I got a notice I’ve exceeded something (bandwidth?), but then everything was accessible and no problem. I did go back and delete some postings, so that should free up some more space. I see this, though, as a sign that I need to upgrade to more space, or what? I post quite a few thumbnails, and then some, not much, text describing them. I anticipate adding many more. My plan with hostican and wordpress is the $95/year one. How do I upgrade? And what’s VPS hosting? I’ve tried to get info from the hostican website, but clearly I’m floundering. Thanks!