Use the Edit Breakpoint command to add, remove, and
  modify breakpoints. A list of breakpoints is shown with
  the file name, and, if appropriate, the line number and
  breakpoint expression.
 
  To add a new breakpoint to the active source window,
  select <Add>.
 
  To remove a breakpoint, select the breakpoint from the
  list and then select <Remove>.
 
  To change a breakpoint, select the breakpoint from the
  list and then select <Modify>. After you complete your
  edit, select <OK>.