The Property tab becomes available once the Fixed Assets option is selected on the Main tab.
The option Fixed Assets option is available if the Enable Fixed Asset Management option Accounting option is selected on the Administration > Settings > General Settings Asset Management form.
Using this tab, you can enter the beginning balances of bank and cash accounts.
list the available fixed assets with the accounting details on the date preceding the start of operations in the application.
The Opening Balances Entering (create) document. The Property tab
...
The Fixed Asset subcolumn is intended for listing of the fixed assets which have balances on the date of the start of operations in the application. You can select an asset from the Fixed Assets master data, or you can create a new record. For details, refer to Adding a Fixed Asset. In the Class subcolumn, specify the class of non-current assets to which the fixes asset is related.
...