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 }