Right click on a face and select face properties. Now you can assign any name/id to the face.
Thank you for reply
In macro coding I am not able to select that face since the face identity is in the form
boolstatus = Part.Extension.SelectByID2("", "FACE", 3.16173240555031E-02, 9.42400892645878E-03, 7.31273722482229E-03, False, 0, Nothing, 0)
since I want to select that face from macro code I need any (x,y,z) point over that face. I can get that one for plane surface but in case of curve surface it is very difficult.