How do you authenticate to the BIGIP PPTP, may be a moot question

OK. first thank you everyone for your help it got me this far. I have the PPTP set up and listening. can ping and tracert fine. Now this is going to sound bad (I am new :) ). with a windows box it uses username and password. Does the BIGIP do this? IF not how do you actually test to connect, where do those credentials come from or is this a moot point? I am going through VPN set up and it's asking for username and password. Does BIGIP manage this information or is it like a proxy and get it's information from elsewhere?