How do I write blog articles if I'm not an expert of anything?
The one thing you do not want to do is pretend to be an expert. This veiled effort will be seen through and you will be discredited.
That being said, by doing research about novel writing you can become an expert. There’s a sense in which many writers have become experts by writing about the things they are passionate about. I have written so many blog posts about Bob Dylan at my knowledge shout blog over the past nine years that the public library bound my blog posts into a two volume book. To some extent I am sort of an expert on Dylan, though I am fully aware that I am no Christopher Ricks or Greil Marcus. I do not pose as an expert… but having listened to fifty years of Dylan music and writing hundreds of blog posts about him, I know a lot more than the average person walking on the street.
In your case, you seem to be interested in this topic and here are some ways you can turn your research into blog posts. The blog posts will not be about “creating characters” written like an expert as if you have forty books published, but rather, “Here’s what Stephen King says about creating characters.” “This is John Gardner’s advice about scene descriptions.” Whatever you are reading about novel writing, share it intelligently with an aim to helping people.
You may also try to interview novelists. There are a million books are year being published now and many writers who would welcome the publicity. Most are fairly visible on social media because they want to gain a following. I enjoy interviewing artists and writers, in part to see what makes them tick, and in part to help my readers learn things so they can become better people or learn more about this or that. Start following writers, authors, novelists on Twitter. Ask them how they deal with writer’s block or scene transitions.
If you like reading novels, then write reviews as blog posts, with the aim of teaching something about novel-writing by pointing out to your blog readers how the author generated interest in his or her opening. Or how it’s apparent the author did a lot of research before beginning this massive volume. (e.g.: The first 30 pages of Michener’s Hawaii is about waves.)
You do not have to be an expert to write about novel writing. But if you keep it up, you will become an expert, even if you never write a novel. Sports journalists don’t need to know how to hit a baseball like (name your fave player) to be able to write about it intelligently.
Good luck. And have fun