Just use the default Input Name command. It's on Page 1, [Actor] and it's right above Change Class (Change Name...)
If you want an upgraded version of the Name script, like...a more advanced or cool one...(On RMXP, RPG Advocates and Samo the Thief made pretty nifty ones) I'm afraid I can't find anything to help you there at the moment. I didn't do a thorough search so it probably exists. I assume if it's made, then Wortana made it.