Learn the ropes means to learn how to do something.
Example of use: “Once I learn the ropes at my new job, I won’t be so nervous and I’ll be very good at the work I do.”
Not surprisingly, the origin of the idiom “learn the ropes” is nautical. Before the days of ships powered by steam or fossil fuel, almost all ships had sails. New recruits had to learn how to tie knots and manipulate the ropes that moved the sails to capture wind most effectively; this series of lessons was termed “learning the ropes.”