Hello,
I HAVE A NEW COMPUTER AND I DONT REMEMBER MY NETWORK SECURITY KEY.
The key can be found in your router's configuration. Please reference your router's documentation or manual for this. Beyond that, we can't help you on this forum, as it would be against forum policy.
Look on the bottome of your wireless router and you should see the default username/password and login address. You can then login to the router and reset the password.