Are you referring to the Ovulation Calculator or the Ovulation Tracker? There isn't a way to put the Ovulation Calculator on your home page. It's located in the Pregnancy Community, so if you join the community, it'll show up in your Shortcuts. Then you'll be able to quickly go to the community and click Trackers & Calculators to access the calculator.
If you're referring to the Ovulation Tracker, the tracker should already be on your home page.