My comuter is al ready connect but need to secure it.

Is this wireless? If so to acces the router you need to hook it directly to your computer or laptop with a cable to change the settings. Then you can choose the security that you need.

What exactly are you trying to accomplish?

1. Secure your wireless internet?
Or
2. Secure your router's web interface to prevent people from changing settings?

These are 2 very different things and to be able to help, we need to know which of the 2 you are trying to do.

d-Link