Before using any source in a paper or research project, you need to evaluate it. Besides being a credible and authoritative source, also make sure it makes sense to use in your project. If you're talking about Twitter, you probably won't find good sources to use from before the 2000s. If you find a source written by a manufacturer of televisions, and your topic is TV, you'll want to realize that there may be bias in the article. Watch the two videos below to learn more about evaluating sources, and more about the differences between popular and scholarly sources.
These databases are useful for general information on any subject. Use keywords and think of your topic in broad terms to get started. Narrow your search by limiting the publication date or by adding more keywords.
These are databases specific to the communications field. Use broad searches and note the subject terms and classifications of articles you find that are useful. Read through abstracts before you commit to an article. What may sound promising from a title might not be. You want to find the best sources for your topic, not the most convenient sources or the first hits in your search.