If after all of your capital gains and losses have been entered you have a net capital loss, this loss cannot be used to offset other income. Line 12700 of your Detailed Tax Summary will list your taxable capital gains as zero.

The loss will be carried forward to be applied to future years' gains. Or, if you had capital gains in the previous three years, you can request a loss carry-back to apply this year's loss to those past gains. Assign the loss in the Losses section (Deductions - Losses).