Please see the written information and there is also a video at the bottom of this page showing the process of listing your NFT for sale.
A NFT can be sold on The Karbon Collective Marketplace, the NFT holder can list the NFT for sale at the Floor Price. If there is no buyer for the NFT within 30 days, on the 31st day, The Karbon Collective will purchase the NFT. (once a NFT is listed for sale it will not produce data farming result nor data rewards).
To sell your Karbon Collective NFT/s go to the specific account your NFT is in and click on the shopping cart in the NFT Floor Price section.
This will open up and ask if you would like to sell your NFT. 
Click "yes" please be aware once you list your NFT for sale it will no longer collect Data or generate Data Rewards.
Your MetaMask Wallet will automatically open up and you will need to scroll down and click "confirm" to complete the transfer of your NFT.
You will then see a message on the top right of your screen confirming the successful transfer of your NFT.
