If you installed KiOS on your Raspberry Pi 3, and want to use a WIFI dongle instead of the built-in WIFI, you will need to disable the built-in WIFI first. This is how to do it:
Make root partition writable
By default the /root partition is set to read-only, to prevent against data corruption. However if you want to disable the built-in wifi dongle, you need to modify a file on the root partition. Therefore we will make it writable by enabling debug state. You can do this by editing the /data/etc/os.conf file.
Change the os_debug parameter from false to true. After this you'll need to reboot the system, you'll see that the root partition is editable.
Blacklist internal wifi
After you've made the root partition writable, you can edit following file:
At the end of the file you should paste following lines.
Save the file (CTRL+O) and reboot the system. After the system is rebooted, you'll see that it will connect to your WIFI by using your dongle.