Many moons ago had Guitar Studio - great.  Have just received SONAR X2 as a birthday gift.  Appears just as impressive - but now for Windows 7 platform.
 
O am using a the Line-In to input from guitar/mixer desk/IPad etc..
 
The guide tells me to insert an audio track, and then click the Input drop-down menu.
 
Can anyone tell me where this drop down menu is - does not appear to be explained anywhere in the Guide.  Or am I missing something?
 
Thanks

It is "S" in this illustration of the audio track controls in the track view from here
 

Understand.  But how do I get Track View.  I have tried Views>Track View but does not bring up this display.
 
I can get an I/O drop down option which lists All/Custom/Mix/FX and Track Control Manager.  I can also get Selected Tracks Inputs under the Tracks pull down...but as I cannot get Track View I do not see the same display as above.

This is the track view (from this page).

The illustration in the previous post is a close-up of "C" (track strip) with what you refer to as the "I/O drop down option" set to All and the track strip sized to show all the controls. Track size can be set various ways. One way is to click-drag the bottom of the track.
 
The track input can also be set in the Inspector using the top drop down in "J" on this illustration from the page