Well, obviously one would need to start off with a plan. After having an idea/blueprint of what your ideal treehouse will look like try finding some measurements for the wood (or whatever material you will use I won't judge) of course you better already have the length, width, and height of your treehouse. After that, you can get building; which could take days or even weeks depending on the house design and the amount of people you have to help out. Once that's done you can paint and decorate it all you want. (of course, to get it in the tree you might need a pulley to put it up there or build the bottom up on the tree.) And all your missing your ladder and that's it.
Because the molecules that are being transported is moving against its concentration. gradient. in other words, its moving from where it's low in concentration to where it's high in concentration.
