How can I develop book writing skills? Also, how can I get a book published as an author?

There are many ways to develop writing skills, of which the primary method is to increase reading habit a lot. The more one reads, the more they can write.
Secondly, a creative writer needs to have an analytical view of everything, which makes him/her look at the events occurring around them with the third eye. Reading between the lines matters a lot. This analytical view pushes you to get a new and fresh perception of things that you can present in your prose, poetry, novel or any form of writing.
Publishing a book has become one easy way in the current trend. You can publish a book through publishers like Notionpress who support independent writers and debutants. You can also approach Amazon Kindle, where you will also be able to publish both e-book and hardcopy of your writings.

Any writing skill comes from reading a lot.

1. First step: read and read across genres; fiction, non-fiction, everything. It will get imprinted into your DNA, so to speak, you will begin to understand how writers write & think.
2. Next, find a story or subject of your passion, nurture the thought, and let it flourish. Jot down ideas, plot points and slowly begin to give it a linear narrative.
3. Practice: It is an essential step. Practice writing, even if it's for 20 minutes each day. The more you practice, the better you get at it.
4. Lastly, how to be a published author today? Give your manuscript to a publishing house for review, and if they like it, u are in luck or else self publish ( pls google details too many) and sell your book on Amazon, Flipkart etc.
5. Be a self-published author. It is an excellent option for beginners.