If you do not know how to do this then please refer to OOP Concepts and look under objects, then class.
For those who have not viewed Objects, the private data structure called Person has the following attributes.
1. First name
2. Last name
3. Age
4. Weight
with the following methods or operations for The Person object:-
1. set_first_name
2. get_first_name
3. set_last_name
4. get_middle_name etc..
The top section is were you put the name of the class.
The middle section is for the attributes (your attributes are private), next to your attribute name, you put the data type.
the bottom section you write the operations (which are going to be used to change the state of the attributes)
For those wishing to learn more and get into the nitty gritty about UML notation, a good web site is: Rational Software (UML Resource Center)
For those who prefer to read a book,
The Unifified Modelling Language reference Manual (1991) written by Rumbaugh, J and jacobson, I and Booch, G. Published by Prentice Hall