You fvcking don't.
There's a chance, however so small (about 0.0001 or so) that she will grant you a second chance, but first you want to ask yourself if you really want her, or an experience of a lifetime you could have if you spend all the time you're planning in investing into "getting her back" to living your life like every true man should?
Best of luck to you. Next the b!tch.