First you must link the apaleo's hotels/properties to a Xero's organisation. You can do that in the menu "Xero organisation config". You see all your apaleo's property in the list. In the column "Organisation" you can select the appropriate xero's organisation. You can link more apaleo's properties to one xero's organisation or you can do 1:1 mapping.
Additionally you can define a xero property name for each property. This information will be send with each transaction. The "Property Name" is a tracking category in xero. The name of the tracking category must be defined as "Property Name".