Part of the problem is finding the time, another part is making the time.

I suggest rereading what you have written already and making some notes about where you want the story to go. When you have a good idea of what you want to do, make a little time to write just a small part of what you want to add. If you make a small amount of time every day, it won't take long for you to have another chapter ready to go.

I prefer to use Google Docs because I can use my laptop, tablet and desktop computers to write without having to transfer anything.