You must have your MT-S transmitter setup to bind, and have ENTER highlighted (but don't press yet).
Holding receiver's BIND button, power ON the receiver.
The bind LED will flash slowly.
You can release the receiver's BIND button.
Now is the time you want to press ENTER on the MT-S transmitter.
Receiver's BIND LED will flash rapidly then go out.
After receiver's BIND LED goes out, press ENTER a second time.
Both the BIND LED (on receiver) and the blue LED (on transmitter) will become solid.
Binding is complete when you have solid LEDs

The manual is very specific with binding procedure, and needs to be done with 10 seconds.