the easiest way of getting to praia de charitas from rio's zona sul is via the bus 7003 (also marked 740 d) that leaves from praça general osório in ipanema posto 8, across from the easy to spot zona sul supermarket. 

the 7003 bus also stops in copacabana along avenida nossa senhora de copacabana, at the bus stops marked brs3 - avenida nossa senhora de copacabana is the main avenue one block away from the water.   

during peak hours, it is best to take the bus from the starting point at praça general osório in order to find a seat - travel time from ipanema to praia de charitas, the final point of the bus line, varies between 60 and 80 minutes.