How to fill the O2 tank?

I am just about ready to leave Akua but I can not figure out how to fill the oxygen tank. I have a bunch of tanks but they don't go in there. I am also assuming I can find the other ores on the moon of Akua since I can not make much of a ship with the four ores on the planet.

So long story short, how do I fill the oxygen tank on my ship so I don't die?

Thanks!