How do i find my own security key for my wifi?

Do you have access to your router security settings? If so, you can get there.

If not, who is the administrator for your network? You can ask them.

Discussions on how to bypass security measures are not allowed on Tom's Forums.
 
Your best bet is to change the security key to a new one.

Plug your PC directly into the router using a LAN cable
Look up your router's default IP address
Disable WIFI on your PC
Open an internet browser and enter the routers IP address.

Use the web configuration to change the password.
 
You may need to do a hard reset if you still can't get in look up the model number of your router on the manufactues website and they should be able to tell you how.