This document highlights my quest to install Gentoo with Systemd my Macbook Pro 2015 (12,1). I'm basically following the amd64 handbook with some changes I've had to search out.
First we need to connect to the network. I'm using WiFi to accomplish this and my network is WPA so I run
wpa_passphrase <SSID> <PASS> >> /etc/wpa_supplicant/wpa_supplicant.conf
rc-update add wpa_supplicant default
/etc/init.d/wpa_supplicant start
I'ts probably a good idea to test that the connection worked with ping 8.8.8.8
or something to that effect.