The best way is to make your changes in ItsDeductible, then re-import the information into TurboTax. That way, your ItsDeductible and TurboTax programs are synchronized with each other.
After re-importing from ItsDeductible, review your Donations to Charity in 2018. The most recently-imported information will appear at the bottom of the list.
If any charities were duplicated during the import process, simply remove the oldest (topmost) instance by selecting the corresponding Delete button.