With a set of results in Primo Search, you can use the Show only > Peer-reviewed Journals option to refine your results to articles from peer-reviewed journals.
Some databases offer the option to limit searches or refine results to peer-reviewed journals.
Ulrichsweb Global Serials Directory
The most reliable way to check whether a journal is peer-reviewed is to check in the Ulrichsweb Global Serials Directory:
If you go to a journal website, information on peer-review will usually be included in a section on information for authors or publication policies and procedures. A good way to find the website for a journal is to check the journal record in Ulrichsweb!!