How do I undo deleting my bluetooth device from my macbook bluetooth device list?

Also, most Bluetooth speakers have a pairing routine that will usually be initiated right after turning on, or by keeping the power / pair / connect / play button pressed for a while —which specific button will depend on your speaker make and model; either explore a bit, or find the manual.

In System Preferences under 'Bluetooth', try turning Bluetooth off and then on again. Under 'Devices' your Mac should start discovering Bluetooth devices within range (make sure you are within range of your speakers when you do this).

If that doesn't work, make sure your speakers are connected to power or that their batteries are new/charged.