Well, there are several methods to replace kingroot with SuperSU. One of them is explained here -
1. Download SuperSU-Me app from the links https://sites.google.com/site/androidxdacom/file/supersu-me-v6.7.apk?attredirects=0 or from Google Play Store.
2. Launch the app once installed.
3. When it asks you for root permission, grant it.
4. Once the app is launched, you will see a Android button in blue background.
5. Click on the Android icon. Replacing the Kingroot starts. It can take around 30 to 50 minutes to complete the process.
6. Once the Kingroot is replaced with SuperSU, the SuperSU launches automatically.
You can uninstall SuperSU Me application from your phone now. It will not affect the SuperSU app on it.
Kindly note that this is one of the several such options available for replacing Kingroot with SuperSU.