You don't need a USB port. You connect your PC to the device via an ethernet cable and then use your web browser to navigate to the routers web page GUI. From there you can set the network up.
Refer to the devices manual.
Key things to look for in manual to be able to access setup page:
Default Gateway or Management IP Address: You type this into the browsers URL bar to access the device
Username: usually 'admin' by default
Password: usually 'admin' by default
Once you have found the management/default gateway address listed in the manual and your router is connected to your computer with the phone line connected to the internet port(only needed for internet setup phase). Set your PC to receive an IP address via DHCP, if successful then move to the next step. If not, set it to a static IP address within the network range of your router.
Once in you have all the info and have logged into the router setup GUI in your browser then do the following:
Home routers usually have a setup wizard, follow it and you will be prompted to enter you ISP user account credentials.
This is just a very vague guide outlining the general process. If you actually follow it you may become lost so for a more detailed and router specific method I would follow the manual! They usually include a step by step setup guide.