How can I travel from Shenzhen Baoan International airport to Shekou Ferry Terminal?

You can take the airport shuttle bus line 10 to the port directly. The bus fare is CNY8.
Or you can take the bus No. m416 to Hourui Station, where you can take the subway Luobao Line to Window of the World, and then transfer to Shekou Line to the port directly.
It will not be difficult for you. In the airport, there are signs in English showing the direction to take the shuttle bus, and if you take the subway, there are also English broadcasting, you will find is simple.