You need to set up a VPN to access a corporate server in either of the following two situations:
•Your company's wireless local area network (LAN) is located outside the firewall.
•Your company's wireless LAN is located inside the firewall, but you are trying to
access the network from outside the firewall (for example, from a public location or at home).
Check with your company's system administrator to see if a VPN is required to access the corporate network. If you need a VPN, you must purchase and install a
1.Install your
2.Go to Applications 
and select Prefs 
.
3.Select VPN.
4.Enter the settings provided by your corporate system administrator.