1. Go down to the subway station at 42nd Street and 7th Avenue.
2. Take the R train towards Bay Ridge.
3. Get off the train at the Court Street station in Brooklyn.
4. Walk along Court Street towards the river.
5. Cross over to the Manhattan-bound side of the Brooklyn Bridge.
Alternatively, you can also take the A train or the C train from 42nd Street to the High Street station in Brooklyn and walk over the Brooklyn Bridge from there.