It is also asking me to go to the years back (2019, 2018, 2017) but all are 0. I am confused as to why it is referencing previous years (to apply the loss to) or if that the amount was applied to this year and that it would be carrier forward.
Thank you for choosing TurboTax,
As per CRA, If you have a capital loss in 2020, you can use it to reduce any capital gains you had in the year, to a balance of zero. If your capital losses are more than your capital gains, you may have a net capital loss for the year. You can use a net capital loss to reduce your taxable capital gains in any of the 3 preceding years or in any future year.
Therefore, the balance for capital gain field 0 is right. You cannot create a negative balance. You can use a net capital loss to reduce your taxable income in any future year.
Please visit the website on What happens if you have a capital loss? to learn more about capital loss.