In French, just like in English, to make most nouns plural, you simply add -s at the end.
Note that you don't pronounce the plural -s in French.
If a noun already ends in -s or -x or -z in the singular form, then it remains unchanged in the plural form.
Examples and resources
"Les pluriel des noms" by youlearnfrench.blogspot.com
"Plurals in French" by www.frenchspanishonline.com