The National Fuel Scheme started last week (27th September).
Generally, an application for fuel would have been taken at the same time as the application for OPFP (even if it's outside the fuel scheme dates when you apply).
Your local SW office should be able to take an application from you for the fuel scheme. If you have an entitlement to the Fuel Scheme, it won't be paid until your OPFP is decided, but any arrears due will be paid to you at that time (the back-dating mentioned online refers to late claims - e.g. applying in January and seeking payment from October).