D-Link DIR-508L Faq page 8

Save.
If the connecSon is successful, there should be a green check mark between the Internet
and DIR-­‐508L icons.
Method 3 -­‐ Using a 3G/4G USB Adapter:
Plug your 3G/4G USB modem into the USB port on the DIR-­‐508L.
If your SIM requires a PIN, enter it and click Save.