How do I start my Honda 2017 Fit...the battery is fine

There is no "key ignition" if you have an EX or EX-L model with a start button. The button can be a concern, however that's not for certain. Start by checking the battery (I know you said it's "fine" -- but still check it professionally). Then check the battery cable connections and condition as well as the starter motor and other related parts. Hands on testing is needed, part by part. Use this link to find some shops near you that can help with your concern: www.repairpal.com/repair-shops