When using in-text citation in MLA Style, use parenthetical citations. Typically, the source information will appear at the end of the sentence (just before the period) in parenthesis; however, there may be situations in which it is acceptable to place the parenthetical citation elsewhere in the sentence, or to omit the information.
In-text citation
According to John Wiens at the University of Arizona, we may not be able to save all threatened species; however, we can save many and "cut the number of extinctions in half" (Page).
Corresponding entry on the Works Cited page
Page, Michael Le. “How Climate Change Hits Nature.” New Scientist, vol. 250, no. 3329, Apr. 2021, pp. 41–45. EBSCOhost, https://doi.org/10.1016/s0262-4079(21)00615-1.
The source information included within parenthetical citation depends on the source medium (print, web, etc.) and the source's entry on the Works Cited page.
The in-text information must correspond to the source entry on the Works Cited page. The signal word or phrase you provide in text must be the first thing that appears on the left-hand margin of the corresponding entry on the Works Cited page.
In the example above, you can see the the author's last name in the in-text citation and it is the first word in the corresponding entry on the Works Cited page.
The idea is to make it easier for the reader to match the information for further research. Think of the corresponding in-text citation as a map to its corresponding entry on the Works Cited page.