It's quite easy to get tied in knots when dealing with the early stages of an Arch install because you're offline. So what do you do about this? Get online ASAP. Sometimes via ethernet, sometimes WiFi is the only option. Here's a quick set of instructions including a couple of gotchas that might help you.
This guide was written with Arch in mind but will just as well work with any modern Linux distro.
killall dhcpcd wpa_supplicant wpa_passphrase SSID passphrase > /etc/wpa_supplicant/interface-name.conf wpa_supplicant -B -i interface -c /etc/wpa_supplicant/interface-name.conf dhcpcd interface
Either reboot or killall any leftovers from your previous hacking to ensure you begin with a clean slate. Common things are:
killall dhcpcd wpa_supplicant
Generate a configuration
On my Thinkpad the wifi interface is named
wlp58s0. I can find this with
ip link and looking at the available devices.
I know the SSID and passphrase of the wifi in question. I also know it is WPA2. Using
wpa_passphrase we can generate the required config.
wpa_passphrase SSID passphrase > /etc/wpa_supplicant/interface-name.conf
wpa_supplicant itself supply
-B for background mode,
-i for the target interface and
-c for the config file.
wpa_supplicant -B -i interface -c /etc/wpa_supplicant/interface-name.conf
dhcpcd to grab an IP address and you should be set.