How to Capitalize first letter in Name field

How to Capitalize first letter in Name field

I am trying to capitalize the first letter in the First and Last name fields.

Name = (input.First_Name.toUpperCase()).subString(0,1)

When you enter the name only the first letter of the name is displayed in CAPS but the rest of the name is not accepted int he field. So the result for example with the name Kimberly it will only execept K in caps. What am I doing wrong?