On that lens, there are a couple of switches, one turns OIS on or off. The other switch has two markings, one is A and the other marking looks sort of like a shutter. Sometimes, this switch sticks, so make sure it is definitely moved to the shutter icon side (Move it back and forth a few times to make sure it moves freely.). Once it is in place, you should be able to change the aperture by turning the ring and have the changes listed in the evf or lcd.
If the switch is on the A side, the camera controls the aperture and you will not be able to change the setting.
p.s. Welcome to the forum.