Note: before proceeding with steps below, set adapter bindings by following instructions here. Also insert operators sim card that does not work with device. For example if it's locked to operator "A" insert operator's "B" sim. Connect device to PC using USB cable

Launch DC-Unlocker client

Open Server tab, enter your username and password that you received after credits purchase. Click "Check login". (you can buy credits here www.dc-unlocker.com/buy).
If DC-Unlocker/Vygis/Rocker/Infinity dongle is connected, only click " Check login ".

Note: if you can't login or get error connecting to server after connecting Huawei E5776s to PC, check these settings here

Detect device by selecting Huawei modems from manufacturers drop down menu list, leave Select model as auto detect (recommended) then click magnifying glass button.

Wait till DC-Unlocker fully detects modem

Open Unlocking tab, click “Unlock”. If there are more options below "Unlock / "Do job" button then leave it as it is selected by default

Wait till you see a message that device was unlocked

After you see that device was successfully unlocked, restart it. Now you can use it with any SIM card.