It's as simple as that. Write about absolutely everything, especially if it's something you don't think you want to write about. Challenge yourself to express something new. Even if you don't like what you came up with, at least you tried; every mistake is a learning curve, particularly in a pursuit as personal and subjective as writing.
If you need something to kick start your creative juices when it comes to writing about anything and everything, try TypeTrigger, linked below.
This website provides random 'triggers' and challenges you to write a short (300 words or less) piece about them. It provides a platform for you to practice these little skills as well as a community of similarly minded people to read your work and help you reflect on it.Source: http://www.typetrigger.com/