You can trade through supported brokers in Medved Trader without having to go to your broker's web site. In order to do that, you have to set up the trading accounts first.
To do that, you would go to Settings - Trading - Accounts, select your broker and create an account entry, specifying the parameters that are needed for Medved Trader to authenticate you to your broker, submit your orders and receive information from your account in order to display it to you.
NOTE: all login and authentication information, trades and account information are communicated directly between your computer and your broker. None of this information ever goes through Medved Trader's servers and the best encryption algorithms are used for this communication. It is exactly the same as your web browser communicating to your broker's web site.