get in(to) the swim (of things)

To become actively involved in and knowledgeable about something. It took me a few months to adjust to my new job, but now I'm really getting into the swim of things. I want to get in the swim before I come back from leave, so I've been asking my team to start sending me updates on all our projects. Lucy hasn't had to process expense reports in years, so it will take her time to get in the swim of things.