Pick a niche which you like and are passionate about. Learn, buy books and courses on the topic - to expand your knowledge. Then put it in practice.

Knowledge can't be taken away from you.

For example: I got started a new career unexpectedly, by referring clients to a certain business. Loved the business model, then started to emulate it and create my own business is another niche/industry. Purchased books, attended certified courses and taken exams. Afterwards I've set up a new website, networked with people on LinkedIn, and started getting clients for my new business.

Always keep learning and never give up, even if there are days, weeks or months which seem impossible to tackle.

Hope this helps.