How to sync my invoicing app to my quickbook account

Hi there, zia3179. 

Thanks for dropping by the Community. How to sync your invoicing app depends entirely on which app you're referring too. For instance, if its the Google calendar app, you can check out the following steps:

Get Invoice with Google Calendar app within QuickBooks Online:

1. From the left menu select Apps.
2. Select Find Apps.
3. Search for Invoice with Google Calendar, then select the App.
4. Select Get App Now.
5. Follow the prompts to complete the process.

Get the Invoice with Google Calendar app within Intuit

1. Log in to the Intuit App Center.
2. Search for Invoice with Google Calendar, then select the App.
3. Select Get App Now.
4. Follow the prompts to complete the process.

Once connected, the Google Calendar app will ask you to choose the default service you prefer when applying the recorded time from Google Calendar to an invoice. Follow these steps if you need to modify this setup:

1. From the left menu select Apps.
2. Select My Apps.
3. Locate the Invoice with Google Calendar app card, then choose Settings from the drop-down to open the Intuit App Center.
4. Select Change in the Default service item and rate section.
5. Choose the desired service item from the drop-down (price rate is associated with the item and will need to be changed in the Products and Services list within QuickBooks Online).
6. Select Save and close.

Invoice with Google Calendar: For more information, see Set up and use of Invoice with Google Calendar. If you have any other questions, feel free to post down below. Thank you for your time and have a nice afternoon. 

@zia3179 

Which invoicing app do you have?