How do I actually get on-board the cruise ship?

When you have checked-in and gone through immigration, follow the ship staff and signs.

Once you have dropped your luggage, go through security, check-in and immigration (when applicable), then you can either follow the signs & staff members. These will guide you to the ship or you might be directed to a temporary waiting area until your boarding time. 

On your way to the ship, you will encounter the ship's photographer asking you to pose for a picture. These photos will be available to purchase on-board and if it is not for you, just say "no thank you". 

The terminal gangway (elevated ramp) or the ship's gangway will allow you to get on-board your cruise ship. There the security team will check for your cruise card and in some cases your ID documents again. 

You will probably enter in a public area, in most cases next to the atrium where you will find staircases and elevators. Crew members will be available if you have any concerns or you need help to find your cabin.