It doesn't matter what you write about. Just start writing. The more you write, the more you'll come up with more ideas for what to write about. Start with the rain, the sun, the paperboy, your favorite food, your annoying neighbors, anything. Once you see those words on the paper, you will want to make them better. Rewriting is the goal, at this point.
Writing is a process. The beginning is where you just slap those words down on the paper (or computer screen). Don't worry about spelling or grammar or anything except telling, describing, reviewing or suggesting, whatever! Let the words flow. Do this, freely, unencumbered for a period of time.
Now read it over. Move stuff (ideas, words, paragraphs) around on the paper or screen. Rewrite. Throw out what you don't like. Add more to it. Walk away from it. Come back and read it again. Rewrite. Love what you're doing. Make a game of it. Wallow in the process.
Don't worry about how much time you're spending. Unless, of course you're getting paid and have a due date. If so, you probably already are familiar with the process.
BTW, do you read a lot? If not, make it a practice to do so. A lot of ideas for what to write about can come from or because of something you read. Good luck!