My wife is an Ethiopian citizen living in Malaysia how do I apply for SAR Hong Kong visitors visa

Your wide as Ethiopian holder must apply for a Hk visa from the local China emabssy or consulate even if she will just transit Hk and remain on the airside. You, as a Malaysia pasport holder don't need any visa to Hk for up to 90 days. Your daughter is also visa free to Hk for up to 90 days in HK.