The initial Session dialog consists of several consecutive pages:
On this page, you can open an existing session. You can also
open any snapshot of a
particular session by clicking on the arrow next to the session name to
display all snapshots, and then selecting one. If your session is
not displayed in the Recent Sessions list, the Other
Sessions button will bring up a file selection dialog to navigate
your hard drive.
Alternatively, you can opt to create a New
Session.
Here you can type in the name of a session, select a folder to save in, and optionally use an existing template.
Under Advanced Options, you can select whether you wish to create a Master Bus, or a Control Bus, and how many channels you wish either to have. You can also decide whether you want Ardour to automatically connect all inputs to the physical ports of your hardware. Ardour will do so sequentially and in round-robin fashion, connecting the first track's input to the first input of your hardware and so on. When Ardour has used all available hardware inputs, it will begin again with the first physical input. You can limit the number of channels on your physical hardware that Ardour uses.
By default Ardour will connect all tracks and busses to the Master Bus if there is one. However you can also tell it to automatically connect each output to the physical outputs of your interface or sound card, and limit the number of physical outputs used, as above.
This page is not displayed if JACK is already running when you start Ardour. It provides a simple interface to configure JACK, which will then be started by Ardour. For more control and options regarding JACK, it is recommended that you start JACK before using Ardour, via a JACK control application such as QJackCtl (sometimes called "Jack Control"), JackPilot, etc.
If you are using an Intel Mac running OS X and the builtin audio interface, you must first merge its separate input and output devices into a single "aggregate device" before Ardour will be able to use it.