How do you write a name that ends with an s to show something belongs to them?

There are two accepted forms for possessive singular nouns (common or proper) ending in s:

Add an apostrophe s ('s) after the existing s at the end of the Word.
Examples:
Jess's mother drove me home.
Cross's Market is just down the street.

Add an apostrophe (') after the existing s at the end of the Word.
Examples:
Jess' mother drove me home.
Cross' Market is just down the street.

Note: The -s's is the most commonly used form, but if you are a student, use the form that is preferred by your teacher.