"Community" and "psychology" are very common words. If you search them, you may find too many results. If you want articles written from a community psychology perspective, consider typing "community psychology" (in quotes) to indicate that you need articles with that specific phrase. Also, consider adding a subtopic (such as nutrition or sexually transmitted diseases) to narrow your search.
Use each database's thesaurus or subject headings list to identify the best wording for your topic. For example, PsycINFO uses: