How to start with DDD when you have a monolith

I'm an engineer on biotechnology that did a turn in the lab carrier to follow my instincts and get in to the software industry. Even in the university I was always the teacher assistant in the IT engineering program, but my love for the biotechnology was bigger in that time. After I graduate I realize that the only places where I was able to work were in labs, and always using very old software programs, so I become a developer (after a few hard study sessions) and I'm planing in the near future, join or start a company that mixes biotech and software. I love to do software and I love to be an engineer on biotechnology an a woman in tech and that diversity can relate in software.