Cleanflight wont flash onto SP Racing F3 FC

I need help, i have been trying to flash cleanflight onto my SP Racing F3 FC but it keeps showing ; 2017-12-25 @ 13:04:14 – Failed to open serial port. Is there a way to fix this?

Hey Kamran,
It would be nice, if you check out Posts about this topic that already exist.
At Example:

Luca :slight_smile: