How do I get back to the screen to enter more 1099-b transactions?

Form 1099-B in TurboTax Online will go in Wages and Income, from the menu on the left.

1. Scroll to Investments and Savings and click on Show More
2. Select Start or Revisit for Stocks, Cryptocurrency, Mutual Funds, Bonds, Other (1099-B)
3. Select to Add Investments and Continue
4. Select the type of investment on your Form 1099-B and you may choose to import the form, scan and upload it, or enter it manually. 
   
   On the Your investments and savings screen, there is a button on the bottom left to add investments.