1. Crew

The first button to explore is the Crew button which looks like this:

Clicking this area of the screen will summon the Crew screen, as pictured here:

Here you will see all your crew, their experience progress, and their Rum Meter (if they are the Captain). When the blue line (the Pirate XP) is filled all the way, then you can pay some gold coins to upgrade that pirate to the next level.

The Rum Meter indicates your current captain's level of "Drunkenness". The Rum Meter fills when Rum is consumed and recovers 1 point each hour.

You can also set and remove captains on this screen. Captains gain XP 10% faster then other crew. This may change in the future, but it is worth keeping in mind for now. Setting a captain will start an 8hr cooldown timer before you can set another.