If you're searching for articles in certain databases, you can limit your search to peer-reviewed sources simply by selecting a tab or checking a box on the search screen.
If you have an article, an indication that it has been through the peer review process will be the publication history, usually at the beginning or end of the article.
If you're looking at the journal itself, go to the editorial statement or instructions to authors (usually in the first few pages of the journal or at the end) for references to the peer-review process.
Careful! Not all information in a peer-reviewed journal is actually reviewed. Editorials, letters to the editor, book reviews, and other types of information don't count as articles, and may not be accepted by your professor.
Use the citation format from the American Fisheries Society. Here's an example for a journal article:
Luo, Z., G. Gu and A.C. Wright. 2015. Distribution and characterization of Salmonella enterica isolates from irrigation ponds in the southeastern United States. Applied and Environmental Microbiology and Biotechnology 81(13):4376–4387.
For more examples, see the Transactions of the American Fisheries Society Guide for Authors. Reference formats begin on page 321 of the copy linked below (this is also on your VikingWeb course page).