Since this is almost certainly hydraulic steering and almost certainly you have a fluid leak and it is low at the upper helm, get the Seastar hydraulic fluid kit which includes a plastic bottle and tubing to hook up to the fill port at the helm. Instructions included.
Since this is just affecting the top helm, I would ignore the part about venting the rudder actuating cylinder and simply top off the upper helm. Work the helm back and forth to get all of the bubbles out.
If it fixes the problem then look for the leak. On my boat it was at the lower helm.
David