(chroot) # emerge linux-firmware networkmanager
(chroot) # rc-update add NetworkManager default

The above command will ensure that NetworkManager starts after you boot into Funtoo Linux. Once you've completed these installation steps and have booted into Funtoo Linux, you can use the nmtui command (which has an easy-to-use console-based interface) to configure NetworkManager so that it will connect (and automatically reconnect, after reboot) to a Wi-Fi access point:

# nmtui

For more information about NetworkManager, see the NetworkManager package page.