To connect your new Shivr headphones but it would probably work with other bluetooth headphones too, find the MAC address from your headphones (by connection with an Android device first) and do the following from the command line:
sudo apt install bluez-tools
bt-device -l (that will list the available devices)
bt-device -c AA:11:22:33:44:BB
and make sure you change your Music Player Daemon Output (Audio Volume Settings -> Applications) settings to use your new headphones.