Remove the lid, you won't need that. But you could probably use that for something, a spare palette perhaps? If you are lucky enough to work with extra large tubes, there are larger cases similar to this at Home Depot (or any home improvement store.) I mostly work with 37-40 ml tubes, so this size works fine for me.
Now you will need to take apart the little dividers that are provided. I used an Exacto blade to trim off the little nibs so that the dividers will fit snugly into the slots.
Now all you have to do is insert the dividers into the slots of the box and put in your paint tubes. The tubes will be upright-- less leaking from the lids!
I like having all my reds, blues, yellows and neutrals grouped together. So nice to see all my colors at once!