You need to download the user guide from here
1. Make the computer or network device (for which you are establishing a DMZ link) has a static IP address (or you can use the DHCP reservation feature to ensure the device has a fixed IP address) (see "Set up DHCP reservation" on page 29).
A. Signing up for a Dynamic DNS service (outlined in the DDNS section) will provide identification of the router's network from the Internet.
2. Log into your router management page (see "Access your router management page" on page 22).
3. Click on Access, and click on Firewall & DMZ.
4. Next to DMZ Enable, click Enabled.
5. Next to DMZ Host IP, enter the IP address you assigned to the computer or network device to expose to the Internet.
6. To save changes, click Save Settings.