Balance the equation:

Note: If a chemical species coefficient is "1" then "1" needs to be entered in the field before that species.
__MnO4– + __H+ + __Fe2+ ---> __Mn2+ + __H2O + ___Fe3

is ..

1MnO4– + 8H+ + 1Fe2+ ---> 1Mn2+ + 4H2O + 1Fe3

Answered above.