Make sure no sim is inside device before proceeding to detect/unlock steps.
Connect device to PC via usb and install everything that comes in it's drive (if it has one).
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 "
Detect device by selecting SierraWireless/NETGEAR from manufacturers drop down menu list, leave Select model as auto detect (recommended) then click magnifying glass button
Wait till program detects device
Open "Unlocking" tab, click “Network unlock” button
Wait for unlock to be completed. After that device will restart