Quickbooks has two types of contacts "Vendors" and "Customers". In CMIS any contact that is a "Client" will be created as or updated as a "Customer" and all other CMIS contacts will be created as or updated as a "Vendor".
Navigate to Contacts > Detail View
Find a Client that you would like to add to or update QuickBooks with.
From Actions select Send to QuickBooks
If the contact that you were on was a Client you should be able to find that contact as a Customer in QuickBooks; all other contacts you should be able to find in the Vendor area of QuickBooks.
NOTE: When a contact has been sent to QuickBooks they are assigned a unique number and the number is stored at Detail View > Other > Support as List ID