You should be able to request using points via Manage My Booking in your Qantas account
Noting that for International booking upgrade requests are not processed immediately like they are for domestic.
International upgrade requests are processed in order of Qantas Frequent Flyer membership level, with CL/Platinum One members receiving the highest priority. Confirmations are sent within 7 days for CL/Platinum One members, within 3 days for Platinum members, and within 24 hours for Gold, Silver, and Bronze members.
With so few F seats, Id guess as a NB your chances are are extremely low, unless perhaps upgrading from a fully flex paid J seat as those will higher status will be processed first.