Follow the procedure in this video 

https://youtu.be/Ywn-9rg1oK8


NOTE: there is a great diversity of RC receivers on the market. The video above shows the update procedure with the FrSky X4R receiver but the setps are very similar with other receiver. Just make sure to bind your receiver, enter the correct port settings in Betaflight/cleanflight "PORT" tab and pick the correct receiver settings in the "CONFIGURATION" tab.