When is prime time to ttc?

I am using 3 different <a href="https://play.google.com/store/apps/details?id=com.glow.android">fertility apps</a> on my phone to help me ttc after losing my pregnancy in August. Each app is telling me slightly different dates. This sounds really silly but do you start to try when you ovulate or when your actually fertile? Do the clear blue ovulation tests help? Thank you