I had a capital loss in 2020 of $ 5000 Do I report in 2021 $ 5000 or $ 2500

First off, did you report the capital loss in 2020? If you didn’t, then you will need to adjust your 2020 return to add it. This TurboTax FAQ tells you how: I've filed my tax return. Can I still make changes?

Once you’ve claimed the loss on your 2020 return, you can use any amount that you didn’t use in 2020 on your 2021 return. You can only claim your carried-forward capital loss if you have capital gains in 2021, and you can only claim enough to lower your capital gains to zero.

As per this TurboTax FAQ - How do I deduct losses?, this is how you can claim your losses from previous years in TurboTax Online:

1. Select Find (or the magnifying glass icon) from the top right
2. In the Find window, type Losses and choose it from the list. Then click “Go”.
3. On the Your Losses Profile screen, check off Net Capital Loss Carry Forward, then click “Continue”.
4. On the Net Capital Loss Carry Forwards screen, fill out the fields using information from your Notice of Assessment or Notice of Reassessment from the previous tax year, then click “Continue”.
5. On the Net Capital, Losses Being Claimed screen, enter the amount of loss that you want to claim in 2021.
6. Click “Continue” until you reach the deductions summary, then you are done entering your capital loss.

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