01. Create a new UML diagram
After opening "visio 2007", click "File" -> "New" -> "Software and Database" -> "UML Model Diagram". As shown below.

After creating a new UML model diagram, you will see the screen as shown below. On the left side of the figure are several commonly used graphical elements of UML diagrams.

02. Create a new "class"
Drag "Class" from "Static Structure" to the drawing area; then, set the font size to 14. As shown below.

03. Open the "UML Class Properties" dialog box
Double-click "Class 1" in the drawing area to pop up the "UML Class Properties" dialog box; and change the class name to "int". As shown below.

04. Create "int class"
Click "OK" to create the "int class". The shape of the created "int class" in the drawing area is as shown in the figure below. Just like that, a very simple class was created successfully!

Let's create a slightly basic class Student. The Student declaration is as follows:

public class Student {
private int id;

public void setId(int id);
public int getId();
}

01. Open the "UML Class Properties" dialog box.
Steps 01 to 03, create a new class, open a "UML Class Properties" dialog box, and set the class name to Student. As shown below.

02. Create "Properties".
Click "Properties" in the dialog box, and add the attribute "id" of Student, and set the type of id to int type. As shown below.

03. Create an "action".

(01) Click "Operation" in the dialog box and create a new operation "setId". As shown below.

(02) Select "setId", click "Properties", and the "UML Operation Properties" dialog box will pop up. As shown below.

(03) Click the "UML Operation Properties" dialog box, and add the parameter "id", set the int type of id, and the type is in (input parameter). As shown below.

(04) Click "OK". Return to the "UML Class Properties" dialog box. As shown below.

(05) Click the "New" button, create a new operation "getId", and set its return type to int. As shown below.

04. Click "OK" to close the "UML Class Properties" dialog box. In this way, the Student class diagram is created. As shown below.

05. Save the class diagram as a jpg image.

Files created through visio will be saved in .vsd format by default. The .vsd format file contains the complete information of the file, which can be easily modified next time!
However, sometimes we need to cut out the completed visio diagram separately. For example, save the completed Student above as a separate picture. This can be done by:
(01) Click "File" -> "Save As" to pop up the "Save As" dialog box; then change the "Save Type" to "JPEG File Interchange Format". As shown below.

(02) Click "OK" and the file will be saved as a JPEG image. As shown below.