Problem linking a new object with a contact using import with excel file csv

 Hi, I have this problem.

 

I have created a new object called “Invoiced at hotels” which has information like:

Contact and Total Invoiced.

 

Then I want to import with an Excel file the record:

Contact:John Smith

Tax ID: 12345678A

Total Invoiced:15000

 

But I have this two records as contacts:

Contact1:John Smith

Tax ID: 12345678A

And

Contact2:John Smith

Tax ID: 99999999X

 

How can I tell the system that the contact to update is contact1? When I try to map the Excel fields to the new object fields I don’t see the main Contact fields to link it properly.