Like any other art form (or non-art skill), writing takes discipline. This requires not just studying the craft by reading various styles, genres and authors, but actually sitting your butt down in a chair and putting pen to paper.  This also means carving out a segment of time (such as an hour) at a particular time of day, where you can write, uninterrupted.
Do you enjoy rising before the sun, taking in the cool air and early morning sounds as the world begins to wake itself up?
Take a moment and look at that habit – can you fit an hour to write during that time, while enjoying your coffee or tea? If so, you’ve found your time to write!
Or do you find that it is evening when you’re most creative, after the noise of the day and you’re in the little sanctuary of home?
Again, find that hour, bring tea to fortify yourself (or other favorite beverage) and let the words flow from your pen! 
You may feel that you’re being non-productive at first, especially if no words come, but that’s where having discipline comes in. The more you show up for yourself by creating the habit, the easier it will become to find the words.
You’ve got this – I have faith in you.
 Or fingers to keyboard, if using a computer is your preference.
 Don’t worry if there times when you find writing even one word is problematic – staring into space is part of the process.