usually names of people ending in -an add an s to form the plural.
Italian becomes Italians
Argentinian becomes Argentianians
Mexican becomes Mexicans
Note that plural names of people not ending with s must always be preceded by the, while those ending with s can be preceded by the or not.
French => The French
Italian => The Italian or Italian
For better explanations click here and see point 2c English Grammar
P.s: I'm just a student. If you want to be sure, wait for a teacher.