I bred and showed dogs for years. First I would say don't do it, but since you are determined here is what I can tell you on the matter.
1. Make sure your female is healthy, do not breed her until her third heat. When I say healthy I mean blood work and a Brucellosis test, and UTD on all vaccines since her antibodies will be passed to the pups.
2. The actual heat cycle varies from bitch to bitch so typically the heat begins with the bloody discharge several days later it changes to a straw colored discharge, usually between 7-14 days after you first saw blood she ovulates. That is the time when you allow breedings every other day until about day 16. Typically 3 breedings, the sperm lives for at least 48 hours so she is covered for the next day.
Do not allow the male to just keep breeding her over and over, only put them together until they breed and then separate them and skip a day, You can also chose to AI if the dogs do not get along which can happen most especially with Pits.
3. Lastly I know you are determined but are you prepared to lose your girl if something goes wrong? So many things can happen, dog fight, pyometra, C-section with bad outcome, etc.
I wish you all the best.