Linux users do not have a prepackaged linux program to download to connect to WiscVPN.
Instead, they must get a program called vpnc.
These instructions are written using Ubuntu, but the instructions should be similar.
Using the command line, do an apt-get to get vpnc.
(You have to use sudo to do this.)
Next, cd to /etc/vpnc and see the default.conf there.
Copy that as uwmadison.conf (or whatever you want to name it.)
Edit that file.
Uncomment and fill in the blanks like so...
IPSec Gateway uwmadison.vpn.wisc.edu
IPSec ID (put the shared secret in here)(Use dynamic Shared secret found here...Link)
IPSec Secret (put the shared secret in here)(Use dynamic Shared secret found here...Link)
IKE Authmode psk
Xauth username (put your netid in here)
Save.
To connect, from the command line, type
sudo vpnc uwmadison.conf
To disconnect, from the command line, type
sudo vpnc-disconnect