Huawei-E5577 modem is very handy and sophisticated looking little device modem - but the software running on the device is very primitive. It doesn't even have USB tethering capability but just the WiFi. In order to change Wi-Fi password of the DiGi 4G service in the Huawei modem also not so advance.
This is how to do it.
1. Allow your device such as Phone, iPad, or laptop to access the HuaWei E5577 Wi-Fi network service. Once it is connected
2. In your device browser type http://192.168.8.1 to access the modem portal
3. Click on "Connection Settings" and proceed to change the password
4. Once you confirmed the new password it will reflect on the HuaWei E5577 modem device screen.
HuaWei Wireless Modem IP | HuaWei WiFi Modem IP | How to change Huawei WiFi Modem Password