1) Download, install, configure and connect to the General Use Campus VPN using the Cisco AnyConnect client. Instructions are here...

http://www.cmu.edu/computing/doc/network/vpn/client/

(although there is a download for Linux, and it works, it is not supported. Also, if you have 64-bit Linux, it may fail to install or work, but, I have had success making it work by following these instructions).

2) Once connected to the VPN, proceed to the Platform Identification step.