I sold stocks from an ESPP last year but I did not get a Form 3922. Do I need one to file?

You may or may not be able to accurately file without it. It depends on the details of your transaction and what other information you have.  TurboTax will walk you through how to enter the transactions.  To do so, while logged in and working on your account:

• Click on Search
• Type “1099-B“ in the Search Window and hit Enter
  
• Click on Jump to 1099-B
  
• Click on + Add More Sales
• Answer Yes to: "Did you get a 1099-B or a brokerage statement for these sales?"
• Click on "I'll type it in myself"
• Enter your Brokerage name
  
• Click on the blue link that says "What if I sold employee stock?" for information. 
• Mark the button that says "I'll enter one sale at a time"  
• Enter the information from your 1099-B, then click the blue button that says "Guide me step-by-step"
• Continue to report your sale of ESPP shares of stock.