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@martin:  Before you enter anything, you want to work through the Sales Schedule included with your K-1 to determine exactly what your Cap Gain/Loss should be.  That way, however you do the data entry, you'll be able to verify that you got the right number onto your 1099 and Sched D.  As for filling out the 1099, you say your cost basis was not reported (which is normal), but I assume you actually have a 1099-B from the broker that shows your sales proceeds.  The simplest thing to do is to just enter the correct cost basis on that 1099-B in "Forms" mode.  The correct cost basis is just "Sales Proceeds" - "the Cap Gain you calculated on the Sales Schedule".

Note that if you don't have any 1099 from the broker, so you'll need to create one, AND all your TCP holding were short or long term, you can look TT do the work.  In that case, your "basis" would be what you paid adjusted for the "Cumulative Adjustments" provided on the Sales Schedule.  TT will split that between Ord Gain and Cap Gain, create a 1099-B, and no further adjustments will be necessary.