Before Pairing your device, make sure your Tecla Shield is in the desired mode. If you are not sure what mode you need check here: Tecla Shield modes.
If you are not sure how to change modes check here: Mode Change Instructions.
1. To pair your device go to Apple menu > System Preferences > Bluetooth.
2. With Bluetooth enabled, you should see the Tecla Shield DOS listed under Devices as TeclaShieldDOS-XXXX (where XXXX is a random sequence). Click on Pair.It will change status to Connected. https://support.apple.com/en-ca/HT201171