Editorials and "Op-Ed" or "opinion" pieces provide viewpoints on particular issues, usually controversial ones.  Generally speaking, Op-Ed's are written by named writers who are not affiliated with the newspaper.  Editorials typically are written by the newspaper editorial board, are not signed, and represent the paper's official position on the subject.  Editorial and opinion pieces are most often, but not always, targeted towards current events.  

Tips for finding editorials:

Keywords:
The simplest way to search for editorials is to add the term "editorials" to your keyword search.  For instance, in the database Newspaper Source or Nexis Uni you can search:  "panama canal" and editorial You may also wish to try the words "opinion" and "commentary" as alternatives to the word "editorial."

Date limits:
When you are searching in databases, try limiting the date range to the time period when the event or issue took place.

Database limiters:
Often databases will also provide pre-set limiters that can be chosen before you enter your search terms.  In Newspaper Source you also could have chosen a Document Type limiter of Editorial.  Then searched by the keywords "Panama Canal."