The Windows PPTP client uses the VPN server as the default gateway by default.
Thus, if:
* you haven't changed the default value of "use default gateway on remote network" in your VPN connection settings
* you can still browse the internet after establishing your VPN connection
then:
you *are* browsing "through" your SME server (browse to "
http://whatismyipaddress.com" to verify).
Or, if you're just trying to browse, the instructions in the link you referenced will work.
Otherwise (if you're not using a Windows client, or you want to do more than browse) it would help if you share some more details with us about what you're trying to accomplish.