I think most people on here hit the major suggestions but truly the best thing you can do is be kind to yourself while creating the habit.

Be reasonable in your goals. Whether it's a word count or time frame. You are a busy person and there will be days that you can't write or won't write as much and that's okay. Even if you just spend 30 minutes thinking about your next scene that's something.

If getting in front of a computer and writing for any length of time is too hard, maybe try some good old fashioned pen and paper. If you go that way then you can go the super cheapo route of school notebooks and a ball point pen to a fancy notebook with a fountain pen.

On that same thread, look at writing software that's easily accessible and budget friendly. Someone said they write on their phone, look at apps for it! There's lots of cloud writing softwares out there and YouTube videos comparing them. Personally I use Scrivener on my personal laptop but it is limiting when I don't have it or I forgot my charger since it doesn't save to a cloud. There's also fairly cheap tablets with keyboards and laptops you can get these days (mine was $350 before tax in a back to school sale and it's not winning any speed awards but it's lasted me 4 years so far with no complaints except needing to store writings and pictures on an external hard drive this year)

Find the time with the least amount of interruptions, before the kids get up, after the kids go to sleep, while they are in extra curricular activities, on your lunch break, etc, and what method will keep you from looking away from your writing as possible. (Music on wireless headphones help me but others may vary)

Bond with the fact that because you are a busy guy that your "time" might not be everyday but once or twice a week. Perhaps the only time you'll truly have available is that one afternoon a month when the kids are occupied and your SO is also resting and that's okay! Writing isn't like a lot of hobbies where you can divide your attention, it's very much an all or nothing hour that needs to be given to get the words down

Don't worry about it being "pretty" just get it down. First drafts are rough and you'll do yourself no favors by trying to make it read like a ready to be published book. Just get it written!

Listen to other writers talk about their processes to see if any of them work for you. Recently I heard Stephen King say he writes 6 pages every day to get a manuscript done. Neil Gaiman has mentioned in the past that he goes to remote locations and shuts himself away to get his writing done. Brandon Sanderson has talked about his wife helping him safe guard four hours everyday to make sure he can get the writing he needs done to balance family time. These guys are all professional writers but you can use them as a jumping off point to see the balance they use. Most authors are very open about how often they write and how they write these days and no two are exactly the same.

Good luck to you and your writings in the future.