First, you compile the program using "-pg" option:

$ gcc -pg -o a.out test.cc

or 

$ g++ -pg -o a.out test.cpp

Then run the program:

$ a.out

This will generate a file "gmon.out". We will use gprof to view it:

$ gprof a.out gmon.out

Read the man page of gprof to understand the output.