where to input opening stocks?
Stock > Stock reconciliation > New stock reconciliation
If it is non-serialized item, you can can use above steps. If it is serialized item then you can make stock entry of type material receipt.
In both the case you should enter expenses account as temporary liability.
Note: Make sure you have enabled “perpetual inventory” in stock setting.
Partner for ERPNext
thats what im doing anyway the issue is resolved here https://discuss.frappe.io/t/expense-difference-account-temporary-liabilities-must-be-a-profit-or-loss-account/4246