In the Application definitions within the Client you can choose the login type that will be generated. In this case, choose the "Auto Login" type:

Take into consideration this will only work in a Windows environment and only inside a Windows Domain. You are basically trusting the Windows login to establish identity rather than the application. This also only deals strictly with identity, the user must still exist in the database and have his permissions setup correctly for access.

PS: I'm assuming this is what you mean by "going to the homepage" directly. Because there are other ways to achieve that effect rather than by automatic permissions, like using a different layout or having a public facing module.