If the opening balance in one of your Balance Sheet accounts is wrong, you can open the register of that account and correct it from the Chart of Accounts.

From the home page screen:

1. Go the Company Gear icon (upper right corner) and click Chart of Accounts under Settings.
2. Highlight the name of the account, then click Register button.
3. Go to the top of the register, locate to the Opening Balance entry and edit the amount.
4. Click SAVE. The change will not be saved if you navigate away from the register without saving.

Note:  This Balance Sheet account must be one that you entered an opening balance for when you created it, not continuation of opening balance from prior years.