If you selected Yes to the question "Did you sell stocks, mutual funds, bonds, or other investments in 2020?" you will see "lets get your 1099 form." You should see an option to import this information or enter it manually. If you did not sell stocks, mutual funds, bonds, or other investments in 2020, then you would need to go back and select no to the question:
Where do I enter a 1099-B?