Searching databases for journal articles is a bit more challenging than using tools such as Google Scholar. The good news is that you have a lot more control over how you design your search. This also means you should get better, more targeted results. A search for the question: Does exercise help teenage smokers change their behaviors? could look like this.
You can use an asterisk at the end of a word to retrieve various endings. For example, adolescen* will retrieve adolescent and adolescence.
Other search tips that are useful in searching APA PsycInfo, APA PsycArticles, and APA PsycBooks:
If the full-text of an article is not available in the database, click on the "Find It @ SCU" link to see if it's available elsewhere. If not, you can request the article via Interlibrary Loan. This is a free service and you will usually get the article in 1-2 business days.
Never pay a publisher for an article while you are a student; use your library instead!