How can I tell if I'm entitled to a capital loss carryover from last year's return?

Look on last year's Schedule D, specifically lines 16 and 21.

If the line 16 loss amount is greater than the number shown on line 21 (pretend they're both positive numbers), you should be getting a capital loss carryover on this year's return.

If you transferred data from last year's TurboTax return, your carryovers are already accounted for.