Typically the agency who has the property for sale will be able to have you on the phone with an agent, all you will need to do is to fill out a bidding authority form for them to bid on your behalf
I will just comment on the fees. Typically I find it ranges from $1,000 to $1,500 plus GST to engage a buyer's agent to bid on your behalf. With 50% being an engagement fee and the other 50% charged for a successful purchase.
Typically the agency who has the property for sale will be able to have you on the phone with an agent, all you will need to do is to fill out a bidding authority form for them to bid on your behalf