Here is the binding procedure for F3 Brushed FC (Flysky) . The FC is used on  Beta75S and Beta65S .

Note:  Please make sure the setting in Betaflight is correct. If there is confusion about setting, we suggest you flash the Cli that we shared in our website. 

How To Bind:

1) Connect the drone with battery and press and hold the bind button at the same time Receiver LED (red) with fast flicker which means entering the binding mode. 

2) Choose "BIND" in the transmitter.

3) Binding is successful when receiver LED (red) is off.

4) Power on again, receiver LED (red) is off, which means bind is successful and quad is functional.