Studio allows several options for changing your account or site information depending on which action you are trying perform.
Studio and Foundation 11.
All actions can be performed from the Account tab on the Studio home screen.
For activities that require a different account but on the same Foundation site use the Switch User option. This allows you to specify the account with which to run Studio.
For activities that require navigating between multiple Foundation sites in the same environment (typically Development, QA\Staging, and Production), use the Select Different Site Button.
For activities that require changing from a Foundation site in one environment to a Foundation site in another environment use the Reset Activation option.