To control focus, iris and optical zoom, use the corresponding sliders.
To control focus, iris, and optical zoom, move the corresponding slider up or down.
If the camera has AF (auto focus), you can see the corresponding button under the slider.
Some devices allow to control optical zoom with the mouse scroll wheel.
To control optical zoom with the mouse, go to OnScreen PTZ mode (see Controlling a PTZ Video Camera in the OnScreen PTZ Mode), otherwise the zooming will be digital (see Digitally Zooming Video Images).