If you filed your 2018 tax return with TurboTax and are using the same TurboTax Online account, the capital loss carryover should "automatically" populate in your 2019 tax return. The carryover of you capital loss from 2018 will show up on Schedule D (either Line 6 or Line 14, depending on whether it is short-term or long-term) and on the Capital Loss Carryover Worksheet.
If you need to enter your 2018 capital loss carryover in TurboTax, click the "magnifying glass Search" icon on the top row, enter "capital loss carrryover" in the search window and press return or enter, and then click on the "Jump to capital loss carrryover" link to enter your carryover of capital loss from 2018 to 2019.
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