when you download it, it logs you in: This is a demo version. Once the login fields appear you will automatically be logged in. http://www.interactivebrokers.com/en/software/demo.php?ib_entity=llc
That will not be possible. The demo account has no reliable data-feed and is is generally only a demo of the TWS platform. To do what you want you need to open a normal account with IB and then you get a decent papertrade accoint with its own username as well. This is appropriate for most purposes, but not all: you cannot simulate bid/ask slippage since you limitorder will of course not be published; you only can buy at the ask. Ursa..