Merriam-Webster Dictionary defines plagiarism as:(1)"to
steal and pass off (the ideas or words of another) as one's own: use
(another's production) without crediting the source."
(2)"to commit literary theft: present as new and original an idea or product derived from an existing source."
Avoid plagiarizing by citing the sources you use.
Here are some resources on Chicago Manual of Style that offer help on citing and gives examples for in-text and works cited/bibliography/references:
Zotero is a free, easy to use software that helps you save, manage, and cite research sources.