While on your flotia, access the Shop menu to add to it!
Shop menu in the buildings tab.
Tab 1: Quest items[]
In the first tab of the shop menu is a list of objects on sale, or useful in quests.
Tab 2: Buildings[]
The second tab has buildings both available and locked by price in gold or stars and level. Note, by clicking the i icon, you can see the reward and time required for each building to obtain it.
Tab 3: Plants[]
The third tab contains available plants, as well as farms to farm crops in.
Tab 4: Decorations[]
The fourth tab contains decoration for the flotia.
Tab 5: Castle/island[]
The fifth tab contains expansions to the flotias size, upgrades to the castle, and outer islands all to buy with either gold or stars.
Tab 6: Specials[]
The final tab contains the premium treasure box, which can be bought with stars, and several bundles of stars, keys, and gold and silver bricks which can be bought with actual money.