You can't use HDMI to connect the laptop to the Sony. HDMI-ARC isn't the same as an HDMI input.
Option 1 would be to connect the laptop directly to the TV with HDMI and connect the Sony to the TV HDMI-ARC output. Turn ARC on. You may also have to turn the TV speakers off.
Option 2 would be to connect an HDMI audio extractor to the HDMI output of the laptop. Connect the extractor HDMI output to the display and the optical audio output to the Sony.
Option 3 would be to use the headphone output of the laptop to connect to the aux input on the Sony. This will not sound as good as options 1 or 2 (which are equal in quality).