In case you were searching and couldn’t find exact command to install the wifi-menu (which is usually available during base system install, but not after you’ve rebooted to the newly installed system

), here’s a solution for you:

If you have already booted the system and are connected to Ethernet:

pacman -S netctl

In case you are still booted from the Arch install media, you can mount your new system and then install wifi-menu there with this command (assuming you’ve mounted your new installation to /mnt):

pacstrap /mnt netctl

That’s it. After installation, you should be able to run the ‘wifi-menu’ command without getting the “wifi-menu: command not found”