Peer reviewed articles are published in peer reviewed journals. Some (but not all!) scholarly journals are peer reviewed-- journals that use the process usually have a statement to that effect somewhere. Physical journals might have it in the front or back matter; online journals might have an “about us”-style information page. If you’re looking for articles in a database, you will find that some databases indicate whether the periodicals they carry are peer reviewed. There is a quick way to check without having to find a journal’s submission details-- Ulrich’s Serials Directory tracks details about many publications, including whether they’re peer reviewed.
Use the search box to look for the name of the journal that published the article you are interested in.
Find your journal in the results. If the referee jersey icon appears next to its name, the publication is peer reviewed.