In two words

You must use an Unicode Text File

In details

If you are using a version of Microsoft Excel you could upload and create many certificates with a file in the following way:

Downloading csv example for template in www.retiffy.com

 

 

 

 

  • Edit the file with Microsoft Excel

Edit csv with Microsoft Excel

 

 

 

 

  • Save the file as a Unicode Text (this way you would not have problems with any characters encodings)

Saving as Unicode Text with Microsoft Excel