Raspberry Pi WIFI Conf

Edit the /etc/wpa_supplicant/wpa_supplicant.conf

$ sudo nano wpa_supplicant/wpa_supplicant.conf

Add lines to what already is there, like so:

network={
        ssid="MyHome-A"
        psk="MyHome-A Password"
        id_str="HomeA"
        priority=1
}

network={
        ssid="MyHome-B"
        psk="MyHome-B Password"
        id_str="HomeB"
        priority=2
}