I proposed a girl she say no but I love her. what's the next step to stol his hart?

Its not only your problem that is common for young lover who want to really love someone but she don't want. So according to me once you should wait any turning moment of her life as-
Find out her birthday date and try to wish first.
help her through hide yourself.
if these steps are not possible to go directly on front and say to her reason that why not she like you. If she don't give you any proper reason make sure will come after some day return in your life.
Thanks