If the text (presumably from Word?) already had a TOC, there is no live link to the text.
For a TOC to work automatically, it is based upon text styles. For a TOC to only show say a Heading style, that Heading style has to exist and be applied to only a paragraph that should use that style.
Then once the text is all appropriately styles with paragraph and/or character styles, you need to use what Q calls a List. (Lists have uses besides TOCs.)
That List needs to then use the Heading style (or whatever text style you want to use in the TOC). Using Windows, to access the List palette, you either open Lists from the Edit menu or open the palette from the Window menu. Then you need to make a new list.
The following link may help you understand the process.
http://www.planetquark.com/2010/03/26/c ... arkxpress/