In order to add your Xero account to Briefcase you'll need to navigate to the 'Accounting' tab 'Settings' in Briefcase. Select 'Xero Private Application' in the drop down if it isn't already selected and then download the Public Key direct from Briefcase, or alternatively from the following link: Briefcase Public Key
Once you've downloaded the file please navigate to the Xero Developer website and login: Login to Xero Developer
Select the 'My Apps' tab and once loaded select the button 'Add Application'. Under the Setup an Application panel choose the 'Private' application option and enter 'Briefcase' as the application name. For users with more than one organisation within Xero, Please select the organisation you would like Briefcase to export to. You will need to select the 'Upload X509 certificate file (.cer)' option and select the Briefcase Public Key file you downloaded earlier. Once the file has been selected, ensure you read and agree to the Xero Developer Platform Terms & Conditions.
Now that the account has been created you'll need to copy both the Consumer Key and Consumer Secret Key and paste these back into Briefcase.
Under the 'Rates' tab in Briefcase you'll need to ensure your Rates are using the correct Income & Expense accounts as found in the Xero Chart of Accounts area. To access the Xero Chart of Accounts you'll need to login to Xero, navigate to Settings > Chart of Accounts. You can also setup the default Income & Expense account codes under the Accounting tab in Briefcase.
Tax codes in Xero must match the Sales & Purchases Codes in Briefcase. This setting can be found in the Settings tab of the main navigation, then under the Accounting tab. Ensure that the any relevant tax codes are entered into Briefcase matching the same naming and tax rate as Xero.