i put the wrong amount on my property tax and it wont let me change it

If you are unable to change your input after navigating to the proper place in TurboTax Online, I suggest clearing your cookies and cache (How to clear your cache).  

There are 2 places you can check to edit property taxes. First, in the mortgage interest statement (Form 1098) input, and secondly in the property tax deduction section. ‌Here is how to navigate to each in TurboTax Online:

Mortgage Statement Input:

• Navigate to Federal > Deductions & Credits > Mortgage Interest and Refinancing (Form 1098) > Add/Edit >Choose the bank and select "Review"
• Continue until you arrive at the screen Let's get the details from your 1098
• Edit the amount in the Property (real estate) taxes box 

Property Tax Direct Input:

• Navigate to Federal > Deductions & Credits
• Choose Add/Edit Property (Real Estate) Taxes
• Enter or edit the property taxes paid