Reading scientific articles is a skill that you develop. Unlike a book chapter or magazine article you might read from start to finish, scientific journal articles (particularly research articles) are organized in a way that facilitates a more selective reading process, i.e. skimming and/or reading sections in a different order.
There is no single way to correctly read a scientific article. Even the researchers you're working with (PI, postdocs, grad students) may their own way of breaking down and reading articles, both within and outside of their field. Along with asking about their practices, here are some other resources:
Abstract: summary of the article
Introduction:
background information and a description of the author’s purpose
Materials & Methods:
how the study was performed with enough detail so that other scientists could repeat the study
Results: includes new observations, data and findings
Discussion: a description of what the findings mean and their implications; address potential criticisms
First, skim the article. Read the abstract and skim the Introduction and Discussion.
Second, read and take notes. If you think the article will support your topic, then read the entire article. Be sure to take good notes.
If you can answer the following questions about the article, then you have a pretty good understanding of it.