First, understand that the user experience design is across multiple industries and areas – software, service design, retail, hardware, you name it. You should focus on the domain that you want to focus your user experience design efforts in and learn as much as you can in that domain. If it's hardware, spend time understanding industrial design and production methods used to ship physical products. If it's retail, learn the rules around merchandising and crowd patterns. And so on.
Then, learn and read about some tactics and best practices in user experience design. Learn how to do user research and ethnography, create personas, do usability testing, document designs, create prototypes, etc. Most of these practices can be applied across multiple domains, and yo can apply them whatever you "land" in your career.
Next, focus on your listening skills and empathy. The more you listen the more you understand the needs of end-users and empathy allows you to design solutions to solve their problems, and not just designs that "look good."
Finally, do the work. Don't wait for an opportunity to do UX design, just start doing it. Accept that you are going to be wrong and then get more "right" as you iterate and learn. Learn by doing.