A peer-reviewed article is submitted by an expert in the field to the editor of a refereed or scholarly journal. If it fits the criteria of the publication, the editor sends it out to scholars in that field who evaluate its importance, quality, and accuracy. During this process, the author can be asked to make revisions. When it is deemed scientifically valid with reasonable conclusions, the reviewers send it back to the editor who makes the final decision for publication. A peer reviewed article goes through a rigorous process to determine validity.
Some scientific journals use a layout, called "IMRaD":
You'll need to find an article in which the author or authors describe a study or experiment that they actually conducted themselves.
When looking through articles, keep an eye out for the following:
Language in the abstract like "In this study..." and then a description of the study they conducted.
In the article itself, you'll see sections like methods or methodology, results, and discussion, in which the authors describe the study.
Examples from OneSearch: