To set a new JoyCon using the Shift console, just slide them into position on either side of the Shift hand-held unit.
If that is not an option, browse to the Change Grip / / Order segment of this Controllers menu in your home display. While within this window, press the Sync button between the SL and SR on each individual Joy-Con (minus the bumper railings attached).
The Best Way To Sync the Pro Controller using the Nintendo Alter
Contrary to the Joy-Con units, which may be attached directly into the faces of the Switch, the Guru Controller must be connected to the Switch Dock or handheld via a USB-C cable.
To sync the Pro Controller without attaching it to the Switch, then just navigate to the Change Grip / Order menu and then press the Sync button towards the very top of the pro-control.