It is currently not possible to import payroll data into Xero via CSV, only invoices are permitted by Xero. 

If the Xero Export has been enabled for your environment, it is possible to export Invoices to a Xero-compatible CSV file. If you're not sure whether you currently have access to the integration, please contact Support.

If you are new to Xero, we would recommend first taking some time to get familiar with Xero and it's concepts. Getting started with Xero