To open harbor and gourmet boxes received from daily log-in and missions, go to your “office,” click on the your secretary, then press “supply box”
Food temporarily gives a buff to certain ships in your fleet.
To use cafe, go to “setting,” select your chef, and press, hold, and drag atleast one food item to one of the boxes on the left. If yours behaves anything like mine, it is a giant pain and you won’t see it move across the screen. Once you do that, back out of setting and press the food in the box above the bar to use. You start the game only with navy baked beans. Completing the tutorial line of quests gives you access to La Tio. As I understand it, the other foods can be found in gourmet boxes (with RNG on your side) however I haven’t been fortunate enough to confirm this. These boxes come from special quests and a couple of the more difficult weekly ones.