You can purchase a cruise line transfer. If you purchase your air from the cruise line it will be included. A cruise line representative will meet your plane. If you purchased your air on your own then you can purchase a transfer, separately. Contact your travel agent and they will arrange for the transfers. There will be a charge for this. I cannot give you the exact charge.
In regard to taxis, you would need to follow the signs for ground transportation and taxis.
Most cruises also allow you to purchase a transfer from the ship, after the cruise, from the pursers desk. You can purchase this during the cruise.
When you leave the ship you will pick up your luggage and then be directed to the bus to the airport. If you are doing a taxi I suggest having a porter handle your luggage and get a cab for you. It's worth the tip, especially if you are not familiar with the port.