Account mapping is used to map allocation codes in Autotask to GL codes in Xero.

From the Navigation panel under My Accounting Toolbox -> ConfigurationĀ 

Sales Account Codes

Autotask codes are displayed in the left hand drop-down box and Xero codes are in the right hand drop-down box. Once a code is mapped it will display in the grid below.

Purchase Order Account Codes

Setup your account codes for purchase orders only if you are going to use the purchase order module. The same process as linking a sales account code, except you use the Purhcase Order tab.