How to ship and pay for shipping for my item after its sold on eBay?

The boxes you need are free at the post office, you don't even wait on line, just grab a couple and leave. It is a flat-folded white box with red and blue printing on it that will say "small flat rate box priority mail".

Once you have the box, you have 3 choices for how to ship:

1. Use eBay to print the mailing label, it already knows the rate and will charge you based on what you selected when you made your listing. Then you just tape the label to the box and drop off the box at the post office (don't put it in an outside mailbox, instead put it into a slot or bin inside that actually takes parcels).

2. Bring the box to the post office with the shipping address written on it, and wait on line, and pay to send it via priority mail.

3. Same as above, but use the automated machine that lets you ship stuff (if they have one), and buy the stamp for priority mail small flat rate box, stick it on, and put the box in the bin.

"I'm set on a 'Small Flat Rate Box - Priority Mail'"

Why? Many items that can fit in a small flat-rate box weigh 13 ounces or less, and thus can be shipped at the same speed for half the price using First Class Package.

Also, if you pay at the Post Office instead of printing the label online, you're wasting a lot of money as well as time.

Since your buyer is paying $0 for shipping, it would be wise for you to ship the most economical way.

Priority boxes are free online (not sure if they're free in store). After the buyer pays you then you click on "print shipping label" make sure the weight is 100% correct because if it's not then the buyer would have to pay the rest of the postage. If you don't have a scale then go to the PO and let them put the label on it (you pay cash). If your shipping something small (like a video game) then i suggest first class mail because it's cheap and can fit in your mailbox so the mailman can pick it up.

the box is free.

you have to go to the post office and get a few (you can take as many as you want) pack up your stuff and bring it back to the post office to ship.

Flat rate boxes are free.