Whenever you quote, paraphrase, or summarize the findings or ideas that aren't your own, you need to attribute that information to the original author(s) it came from. Failure to do so is considered plagiarism.
Attributing information to another author is done by what is called citing or referencing that author. Depending on the style your professor asks you to use, this may be accomplished by using either in-text citations or footnotes. You will also be expected to include a list of full citations that describe each work and enable your reader to locate the item. This list may be referred to as References, Works Cited, or a Bibliography depending on the citation style you use.
Each citation style, through different in how they are put together, will include the same basic elements in the full citation:
Author(s). Title of the specific thing you're citing. Title of the larger work the thing was published in. Year/date of publication. Where in the larger work the thing can be found (vol., issue, pages, etc.). Retrieval information.
See below for an example online journal article reference formatted using different popular citation styles:
Morales CL, Traveset A, Harder LD. Sterile flowers increase pollinator attraction and promote female success in the Mediterranean herb Leopoldia comosa. Ann Bot. 2013;111(1):103–111. doi:10.1093/aob/mcs243.
Morales, C. L., Traveset, A., & Harder, L. D. (2013). Sterile flowers increase pollinator attraction and promote female success in the Mediterranean herb Leopoldia comosa. Annals of Botany, 111(1), 103–111. https://doi.org/10.1093/aob/mcs243
Morales, Carolina L., et al. "Sterile Flowers Increase Pollinator Attraction and Promote Female Success in the Mediterranean Herb Leopoldia Comosa." Annals of Botany, vol. 111, no. 1, Jan. 2013, pp. 103–111. EBSCOhost, doi:10.1093/aob/mcs243. Accessed 6 January 2020.
Morales, Carolina L., Anna Traverset, and Lawrence D. Harder. "Sterile Flowers Increase Pollinator Attraction and Promote Female Success in the Mediterranean Herb Leopoldia Comosa." Annals of Botany 111, no. 1 (2013): 103–11. doi:10.1093/aob/mcs243.