The best thing is to join a team of professional engineers that have or plan to introduce CI/CD, code reviews, versioning, and other modern practices. It can be a job or an open source project.
You need to see how to do such practices in real projects, experience the whole process, learn and get feedback from experienced people.
You can learn something on your own from books, articles, adopt and follow them on your pet projects, but comparing to working in a team this will be less efficient.