+Watermelon Lizard System Preferences --> Bluetooth, hover your cursor over the device you want to remove, and an X should appear on the right side of it.
+Caela Sayavong I just sorted it out. Try this Caela: Go to the Bluetooth settings on your mac like it shows in the video. THEN turn your headphones to pairing mode before anything else. This should make them show up as on option on your mac and you just click on it.
+Huongxeng Chang its not the apple product its the headphones your using if they arent that good of quality they wont work well i have pretty ok ones and they work fine on my imac 20