You'll need to use two adapters to connect your MacBook (Retina, 12-inch, Early 2015) to Ethernet.
Connect your Ethernet cable to an Apple USB Ethernet Adapter or a third-party adapter. Then, connect the adapter to the USB port on any of the following USB-C adapters.
Connect this assembly to your MacBook in order to access Ethernet.
*The USB-C Digital AV Multiport Adapter and USB-C VGA Multiport Adapter are powered. These are recommended so that you can charge your computer while also connecting to Ethernet or other devices.