You can pair your smartwatches to the Mac using the Bluetooth Preferences window.
Select Bluetooth Preferences from the Bluetooth icon on the menu bar or choose Apple menu > System Preferences and click the Bluetooth icon.
Then, on the watch, start scanning for Bluetooth devices.
On Android Wear, tap the screen, select Settings > Bluetooth devices > Scan for Bluetooth devices.
On the Pebble just click 3 times on the right middle button.
In few seconds either the watch or the Mac will find each other. Click Pair on the Mac or select the Mac on the watch and accept the dialog that pops up.