Or networkmgr, which will install the gnome 'Network Manager' tool, which will give you a familiar GUI. So 'pkg install networkmgr'.
Or you can generate a copy of wpa_supplicant.conf directly by running 'wpa_passphrase'.
So if your network ssid is "bilbobaggins" and your password is "password", you would do something like
$ wpa_passphrase bilbobaggins password
network={
ssid="bilbobaggins"
#psk="password"
psk=b1ef0550f20f651c7dc5b4637d0b7c91688cd5809883cdf581bf67ff3dcb76d9
}
Of course you will want to delete the comment line that has your unencrypted password.
Then copy that output to /etc/wpa_supplicant.conf (save the old one first), and then run 'service netif restart' to restart the network stack.