The Joy-Con can be paired to one console at a time. If you wish to use the Joy-Con on another console, they will need to be paired to that console.
How to attach the Joy-Con to the console:
Make sure the Joy-Con are correctly oriented.First, ensure the LCD screen is facing you. To ensure the right and left Joy-Con are positioned properly with the console, align the "-"symbol on the left Joy-Con with the top left corner of console, and align the "+"symbol on the Joy-Con with the top right corner of the console.
Attach the Joy-Con to the Nintendo Switch console.Use the rail on the side of the console, and slide the Joy-Con from top to bottom, until you hear a click.
Once the Joy-Con controllers are attached to the system, they are registered, and can now be detached and used.
How to detach the Joy-Con from the console:
After detaching the Joy-Con controllers from the console, be sure to attach the Joy-Con straps before starting a game or software.
Press the release button at the back of the Joy-Con while sliding the Joy-Con from bottom to top.
The Joy-Con registration information is not deleted when the Joy-Con controllers are detached. You can now use them as wireless controllers.