Leif,
It is center weighed, metering the central part between the ends of the cross hair lines on the focussing screen, a bit biased towards the upper bit.
It depends a bit on what lens and what screen are used.
There are few controls, so easy to explain.
First, the battery goes in on the front. The small tab is the battery cover lock.
The knob on the other side on the front is the on-button. There is no off-button.
On the left, there are two levers in a circular surround. The display of what they move is on the left of the eyepiece.
The "front" lever sets the ISO of the film in use. Remember to change that when changing magazine loaded with different ISO film.
The other lever sets the maximum aperture ("MAX") of the lens you are metering through. Change that every time you attach a lens with different maximum aperture. And always meter with the lens wide open.
The window on the left of the viewfinder has two lines. Set values so that they appear between (!) the two lines. When setting an intermediate value, not on the scale, set the two adjacent values on lines.
To meter, press the button on the front, and point the thing. The leds will show the EV value to set on the lens.
Should two leds light up simultaneously, use the value in between.
On the right of the viewfinder eyepiece is another window, marked "BAT". It is the battery test window. A green light will show when the metering button is pressed for at least one second. If not, the battery needs changing.