Can I delete HSA information that I entered accidentally?

Yes. First, ensure that your W-2 entry has reported the correct amount of contributions (or nothing if that is the case) in Box 12, Code W.  That is where you and your employer's payroll contributions are entered.  Next, you can delete any separately entered HSA information. Here is how to do this in TurboTax Online:

• Click on Federal Taxes,  Wages & Income,  scroll down to Less Common Income 
• Choose "revisit" 1099-SA, HSA, MSA
• You will see a page titled "Your HSA Summary" which will show any 1099-SA forms already entered.  
• Choose Edit, Continue
• You'll now see a screen that says "Here's what we have so far"
• Choose to delete the 1099-SA