When you sign a contract to buy, your broker converts the pre-approval to full approval.
They will collect a copy of the fully signed contract and Section 32 which is then sent on the lender. A valuation is often ordered.
Once the valuation is accepted and all other conditions are met, the lender issues an unconditional approval and a formal loan offer for signing. Another appointment is scheduled so that your broker can fully explain the loan offer, and you can sign it.
Within 3 or 4 days of receipt of the signed loan offer, the lender moves your file to their settlements area who liaises directly with your conveyancer to book a settlement time on the agreed day.