There are two ways to push contacts to QuickBooks or QuickBooks Online from Core CRM Pro: 
         - If you wish to push a single contact, please see Workflow 1. 
         - If you wish to push a set of contacts, please see Workflow 2. 
 
Workflow 1: 

1) Navigate to the contact you wish to push to QuickBooks in the Contacts module. 
2) Make sure that a Type is specified for the contact. Customers and Leads will be pushed to Customers in QuickBooks. Vendors will       be pushed to Vendors in QuickBooks. 
3) Make sure that the contact has a first and/or last name. Contact pushed from Core CRM Pro to QuickBooks will use a combination       of First and Last Name to label the contact in QuickBooks. (i.e. John Smith). 
4) Make sure QuickBooks and your company file are open. 
5) Press the button labeled 'Push to QB'. 
6) Once pushed to QuickBooks, the contact record's icon will turn green. 
7) You can view the contact in QuickBooks by pressing the 'View in QB' button. 

Workflow 2: 

1) Navigate to the Dashboard module. 
2) Click the side navigation button labeled 'Contacts' to view Contacts. 
3) Apply any filters you wish to have. 
4) Make sure QuickBooks and your company file are open. 
5) Press the button labeled 'Push All to QB'. 
6) Once pushed to QuickBooks, the contacts' icons will turn green. 
7) You can view each individual contact in QuickBooks by navigating to the contact in the Contacts Module and pressing the 'View           in QB' button. 

Course Link:

https://www.productivecomputinguniversity.com/courses/core-crm-pro-training