How do you change a name from ms to mrs?

Mrs (actually an abbreviation of mistress, but pronounced missus) is usually reserved for married, divorced or widow females. Miss is used for unmarried females and ms (pronounced mizz) was introduced as a politically correct Word for more strident feminists who demanded a separate title which did not identify them as married or single.
Ladies become Mrs when they marry unless they insist on ms. There is no legal requirements to change to which term you prefer.