D-Link DIR-506L User Manual page 28

Section 3 - Configuration
If you selected L2TP Connection, you will see the following screen.
Enter your L2TP username, password, and other information
supplied by your ISP. Click Next to continue.
If the router detected or you selected Static, enter the IP and DNS
settings supplied by your ISP. Click Next to continue.
Your setup is complete. Click Connect to save your settings and
reboot your router.
D-Link DIR-506L User Manual 24