To find time to write, you have create the time to write. No, this doesn't mean creating some object to go back in time a few hours so that you can get something done, though that would be undeniably cool. You have to create time to write by prioritizing what you do throughout a day.
One thing you can do is for a day, or longer, if you'd like, write down how much time you spend doing everything. Write down the start and end time of how much time you spend eating, on Facebook, working, completing homework, and writing. Afterward, look at your results. Does your less important stuff add up to bigger amounts of time that you really are doing nothing important during? Maybe you got on Facebook six times throughout the day, but only for five minutes every time. That's half an hour that you wasted, when you could've been writing.
You can almost always find something in your life that you really don't need. Maybe it's that hour you spend on a computer game. Maybe it's watching TV. Maybe it's staring off into the distance because the homework you're supposed to be completing is too boring for you. Whatever it is, cut it out.
Find the most important thing that you won't be able to cut from your life, perhaps work or school, and put it at the top of the list. Then find the next important, and the next, until all those little procrastination minutes are at the bottom of the list. Those things at the bottom of the list can be cut out of your day, thus creating more time for other things, namely, your writing.
It's all a matter of prioritizing. Get what needs to be done, done, and then you can go on and do the other things.