Capture it they way you'd capture normal 24p (advanced or not) footage and then you'll have the property tag (check box) for anamorphic footage. That should make it look nice and good in the viewer window.
Now, this is the important part (I messed this up once and it screwed stuff up real bad later on) Make sure you're sequence is set as an anamorphic sequence as well. You'll have the option to 'checkbox' it. If your sequence is a regular non-anamorphic sequence, the image will look fine and you'll notice the black bars on the top and bottom; this is now like you just shot cropped in camera...that's what I did and it really screwed me up later when I wanted to output an anamorphic DVD file...
So capture like normal, then checkbox both the captured footage and your new sequence as anamorphic.