To sell something on ebay you obviously sign up!
You then create your listing, upload your own photo of the item or use the supplied generic images. In your case you should use tour own image(s).
You then decide whether to set a price for it (buy it now) or set a starting price so that people can bid on it. You can also set a reserve so that if nobody bids at the reserve price or above then it doesn't sell.
You need to decide whether you are including the cost of post and packaging in the selling price, or adding p&p to the selling cost.
If you setup a Paypal account you can get instant payment.
Look out for days when ebay have no listing fees otherwise you will be charged a listing fee.
You will also have a final value fee, and a fee from Paypal for accepting credit card payments - but you could factor these into the selling cost!