You can obtain an officer by inviting your friends to play Battle Pirates!
For every friend that accepts an invite, you will receive a unique officer that you can assign to one of several roles. Each will give you an advantage in some aspect of your combat strategies. Your friend must accept your invitation in order for you to get an officer. If they sign up for Battle Pirates by any other means, they will not be added as an officer.
To invite a friend, you can press the "Invite Friends" button within the game itself.
Once your friend accepts your invitation, you can assign them to an officer role. Officers can be accessed from your Great Hall in game.