how do I show a carry forward loss to this return?

For a capital loss carryover -

Click on Federal Taxes (Personal using Home and Business)
Click on Wages and Income (Personal Income using Home and Business)
Click on I'll choose what I work on (if shown)
Under Investment Income
On Capital Loss Carryover, click the start or update button

Or enter capital loss carryover in the Search box located in the upper right of the program screen. Click on Jump to capital loss carryover