There are several updates, each slightly different, but all based on the same principle..
They can be used both for reflective and incident metering. If you want to measure the light falling on your subject, close the tranlucent white window. Hold the meter near the subject and point it in the direction of the light. If on the other hand it's difficult to measure the incoming light (e.g. the subject is remote), open the tranlucent window, and point the meter at the subject.
As far as metering is concerned; there's an inner disk that you can turn and that shows ISO values in a cut-out window. Set it to the ISO value of the film in your camera. There's a knurled outer dial. Turn it so that the small ring matches the needle in the lightmeter display. You can now read the aperture/shutter combinations that will give correct exposure.
Final remark: the Sixtinos are very nice meters, but they're not robust. Especially the plastic pins that connect the outer disk to the internals are vulnerable and break off easily. Handle with care..