How do we get from Shekou Port in Shenzhen to the Shenzhen-Guangzhou bullet train?

If you want to take the D-trains, you can get out of the port to find the SK Port Subway Station to take the subway SK Line to reach the Window of World Station where you can change to Luobao Line to reach Luohu Station. Get out of the station, you can find the SZ Railway Station and in this railway station, you can find the D-trains.
If you want to take the G-trains, you can take the SK Line to reach Citizen Center Station where you can change to Longhua Line to reach SZ North Railway Station where you can find the G-trains to reach GZ.