If you use MyPost Business or eBay labels, you print your own label and affix it to the package.
If you want AP to generate the label, you need to go to the PO. Which will probably require you to handwrite the address, and pay full price for the postage. Also be careful to make sure your weight/sizes are within the guidelines for the relevant postage. AP boxes and satchels are flat rate up to 5kg, but own packaging is weight specific if over 500g.
The return address is your address, but it would only be a separate label if a buyer is returning an item to you.
It might pay to spend some time exploring AP's website re sending. It is convoluted, but you should be able to eventually find what you are looking for.
