There is a possessive marker suffix -'s. I think you know how to use it already, but you misspelled the suffix. The apostrophe is obligatory when using the possessive suffix.
All singular possessors take -'s regardless of ending.
Roxas's ice cream melted.
Amanda's computer is broken.
Who is looking for Marcus's dog?
Though stuff like "Achilles", "Socrates", "Moses", "Jesus" are controversial due to mismatches in pronunciation and traditions.
Plural possessors take only the apostrophe except if that plural doesn't end with an S.
The cats' food has been stolen.
The employees' cake was ruined.
The children's toys were gone.