The first step in the research process is to think about what you are looking to find. If you have not yet settled on a topic, poking around Google News or Wikipedia can be a good "pre-search" - a way to explore potential topic ideas. This is not what you will be citing as a resource in your paper, rather you are just looking for inspiration at this point.
Once you have decided on something, it's time to brainstorm what the keywords are that capture the essence of your topic. Say you've decided you want to explore the following:
The toxicity of poverty: effects on children's health and well being
Databases are very literal in their interpretation of the words you use when you search them. For example, when I paste that entire sentence into a search box, I see a lot of articles about air pollution and asthma. While some of them may be relevant, it's not exactly what you are after. You need to boil it down to its core and pull out only the words that are salient to the topic you have chosen:
poverty children's health
When you try that search, you will get a lot of hits, but that's when you take advantage of the filters available to narrow things down. The next section will demonstrate how to do that.
As you sort through your search results, pay attention to the words that keep coming up. You may want to add them to your search. Try different combinations of words to see how the addition or removal of certain concepts changes your result set. This is all part of the process.