If you have related an enrolment to a Course of Study for pricing, you can then go on to set up pricing for the individual units of study.
You will need to set up an Invoice Item Merge Template with Unit of Study pricing selected as the context. This determines how the Unit of Study items appear on invoices.
If your pricing structure is always similar for all VET FEE-HELP enrolments, set up a Funding Model with "$ / Unit of study" selected as the Rate Type.
Edit the enrolment and either select your VET FEE-HELP funding model, or allocate pricing items individually against the Units of Study.