First, you have to get the CSV copy of Income tax account Validator via ATO.

Make sure to download .CSV.

Importing income tax account via LodgeiT-

Select "Reports", choose "ATO Accounts" and press "Income Tax Account Validator"

Press "Import" 

Select the .CSV file, then select the button "Import"

Related Article:

Using the Franking Account and Importing Tax & Transactions