i need help about ebay selling?

[Vivi]

Oh my goodness, no, no. You can never put stamps on a package, those are for letters and mails. You put it in anything that fits, so your choice between a large package or a box (although packages are much cheaper). Never put anything in an envelope without bubbles unless it's a letter.
Just wrap it up (your choice to wrap with or without bubble protection) and put the mailing address and your return label. After that bring it to the post office and they'll weigh it for you and you just pay the amount they say!