##How to uncheck “unknown sources” for F-Droid
The other possibility is to let F-Droid install packages using root access (can be found in the F-Droid settings).
First, uninstall F-Droid and make sure you have an F-Droid APK available somewhere, let’s assume it’s at /sdcard/fdroid.apk:
su
mount -o remount,rw /system
cp /sdcard/fdroid.apk /system/app/
chmod 644 /system/app/fdroid.apk
When you’re done, reboot your phone.
You can enter the above commands using an ADB shell or some terminal emulator application directly on your phone.