Your starting point will largely depend on the topic of your research and the types of sources you need. Depending on what kind of research you're doing, you may be interested in:

News on a particular topic

 A specific publication

A specific news article

Depending on the time period, geography, and topic you're interested in, you may also want to search within a collection or a particular publication.

Newspapers: Current & Recent News

Historical Newspapers

Philadelphia-area Newspapers