Why are you trying to enter your investment sales in Forms mode?  Use the interview

To enter an investment sale -

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 Stocks, Cryptocurrency, Mutual Funds, Bonds, Other, click the start or update button

Enter your data through the interview mode.   Go to the Investment Income area and use the 1099-B entry screen.    The data you type in those fields populates Form 8949.   Where do I enter investment sales?