Note: I am by no means an authorized representative of this company. I am someone who has used their services since about 2000 with reasonable success while earning a documented reputation as a trusted seller.
In a nutshell, this is how eBay works:
You post an item for auction.
Once sold, payment is made to your PayPal account and email arrives to announce sale.
At this point you have option of purchasing postage through eBay using funds just placed into your PayPal account. A letter is sent to the buyer with tracking number and proof of postage purchase.
You print postage at home and pack item into boxes provided free by the post office. Once the shipping label is on you may hand this box to any letter carrier or take to the post office yourself. I suggest doing this in person for the details the people at Duncan’s Post Office look at. They’ve saved me from hassle a couple times.
Costs: PayPal currently charges about 3.9% and eBay about 15%
For shipping larger items through different carriers you can use Southern Box Company on Main Street in Duncan. They accept drop-offs and offer professional packing when needed.