If you have chosen one of the conference hotels to stay, you could take taxi directly from HK Airport via Western Tunnel. It costs appx HK$300-400 under normal traffic conditions.
Or you could take Airport Express (MTR or subway in HK) from HK Airport to Hong Kong Station, then take taxi to your hotel.
Please check with your hotel on how you could reach them.
Please having a few hundreds HK Dollars in cash handy when taking transportation in Hong Kong.