How do I connect a Logitech K380 S Pro keyboard to my MacBook Pro's Bluetooth?

I have a MacBook pro purchased about 3 years ago. It has Tahoe OS. I wanted to add an external keyboard

so I got the Logitech pebble keys K380 S.problem is I can't get it to load in my Bluetooth display..I have tried everything. Help please

[Re-Titled by Moderator]

Original Title: BLUE TOOTH DOESN'T PICK UP DEVICE