System Configuration : I/O Setup : Assigning Paths to Hardware I/O

Assigning Paths to Hardware I/O
For more information, see the following topics:
Paths are assigned to specific inputs, outputs, and inserts in the Grid. Paths can be assigned to physical I/O in the Grid, and can be reassigned at any time.
To assign channels:
1 Select (or create) a main path or sub-path.
2 Select the channel Format (such as Stereo).
3 In the row for the selected path, click in the Grid column under an audio interface and channel.
 
Other channels for the path type, if any, fill to the right. For example, when assigning a new stereo path, clicking in the path row under output channel 1 fills both channel 1 and 2 (left to 1, right to 2).
4 Click OK to save changes and close the I/O Setup.
If there are any invalid settings, you will be required to correct them before the I/O Setup will close. For more information, see Valid Paths and Requirements.
Assigning Paths with the Surround Mixer
(Pro Tools HD and Pro Tools with Complete Production Toolkit Only)
When assigning multichannel paths, the left channel (L) is assigned first to the clicked Grid box, and remaining channels fill immediately to the right according to the default path order.
Because some multichannel mixing formats use unique track layouts, Pro Tools lets you set the default format in the I/O Setup (see I/O Setup Options).