How do I put an NFT up for sale?

Open Account → My NFTs, pick the item and choose to sell it. Set a starting price, then confirm two wallet transactions:

• Approve — permission for the auction contract to move the item on your behalf, so it can be handed to the winner.
• List — registers the auction.

You pay a network fee for both. The approval is per collection, so the first sale from a collection needs it and later ones from the same collection usually do not.

Once it is live the item appears on the Market and the countdown starts.